What is Parsing

Two type of Parsing: Hard Parse and Soft Parse

Hard Parse:
If a session executes SQL statement that does not exist in the shared pool. A hard parse is expensive in both terms of CPU used and number of shared pool latch and library cache latch, it needs to release.

Oracle SQL is parsed before execution and hard parse includes these steps:

1. Load into Shared Pool: The sql source code is loaded into RAM for parsing.

2. Syntax Parse: To check any missspelled sql keywards

3. Semantic Parse: Oracle verifies all tables and column names for the dictionary and checks privileges to access the data

4. Optimization: Creates an execution plan based on your schema statistics.

5. Create executable: Oracle build executable files with negative files calls to service sql query.

Soft Parse:
If a session executes SQL statements, that exists in the Shared Pool (i.e : does not require a shared pool reload again).

Reference: http://oracletipstricks.blogspot.com/2008/01/oracle-dba-interview-questions.html

1. Explain database instance ?
A database instance (server) is a set of memory structures and background processes that access a set of database files.The memory structures are used to store most queried data from database. This helps us to improve database performance by decreasing the amount of I/O performed against data file.The process can be shared by all users.

2. What is parallel server?
Multiple instances accessing the same database (Only in Multi-CPU environments).

3. What is Schema ?
The set of objects owned by user account is called the schema

4. What is an Index ? How it is implemented in Oracle Database ?
An index is a database structure used by the server to have direct access of a row in a table.An index is automatically created when a unique or primary key constraint clause is specified in create table command

5. What is a clusters? Explain
Group of tables physically stored together because they share common columns and are often used together is called Clusters.

6. What is a cluster key ?
The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stores only once for multiple tables in the cluster.

7. What are the basic element of an oracle Database ?
It consists ofone or more data filesone or more control filestwo or more redo log filesThe database containsMultiple users/schemasone or more rollback segmentsone or more tablespacesData dictionary tablesUser objects (tables,indexes,views etc)The server that access the database consists ofSGA (Database buffer, Dictionary Cache Buffers, redo log buffers,Shared SQL pool)SMONPMONLGWRDBWRARCHCKPTRECODispatcherUser process with associated PGA

8. What is deadlock ? Explain.
Two processes waiting to update the rows of a table which are locked by the other process then deadlock arises.In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically.These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.

9. What is SGA ?
The System Global Area in a Oracle database is the area in memory to facilitates the transfer of information between users. It holds the most recently requested structural information about the database.

10. What is Shared SQL pool ?
The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.

11. What is meant by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User process.

12. What is a data segment ?
Data segment are the physical areas within a database block in which the data associated with tables and clusters are stored.

13. What are the factors causing the reparsing of SQL statements in SGA ?
Due to insufficient Shared SQL pool size

Troubleshooting,Installation, Unix, SQL,DBA Related

Reference:http://www.oraclepower.com/WebPortal/webportal

PL/SQL Questions:
1. Describe the difference between a procedure, function and anonymous pl/sql block.
Level: Low
Expected answer : Candidate should mention use of DECLARE statement, a function must return a value while a procedure doesn?t have to.

2. What is a mutating table error and how can you get around it?
Level: Intermediate
Expected answer: This happens with triggers. It occurs because the trigger is trying to update a row it is currently using. The usual fix involves either use of views or temporary tables so the database is selecting from one while updating the other.

3. Describe the use of %ROWTYPE and %TYPE in PL/SQL
Level: Low
Expected answer: %ROWTYPE allows you to associate a variable with an entire table row. The %TYPE associates a variable with a single column type.

4. What packages (if any) has Oracle provided for use by developers?
Level: Intermediate to high
Expected answer: Oracle provides the DBMS_ series of packages. There are many which developers should be aware of such as DBMS_SQL, DBMS_PIPE, DBMS_TRANSACTION, DBMS_LOCK, DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_DDL, UTL_FILE. If they can mention a few of these and describe how they used them, even better. If they include the SQL routines provided by Oracle, great, but not really what was asked.

5. Describe the use of PL/SQL tables
Level: Intermediate
Expected answer: PL/SQL tables are scalar arrays that can be referenced by a binary integer. They can be used to hold values for use in later queries or calculations. In Oracle 8 they will be able to be of the %ROWTYPE designation, or RECORD.

6. When is a declare statement needed ?
Level: Low
The DECLARE statement is used in PL/SQL anonymous blocks such as with stand alone, non-stored PL/SQL procedures. It must come first in a PL/SQL stand alone file if it is used.

7. In what order should a open/fetch/loop set of commands in a PL/SQL block be implemented if you use the %NOTFOUND cursor variable in the exit when statement? Why?
Level: Intermediate
Expected answer: OPEN then FETCH then LOOP followed by the exit when. If not specified in this order will result in the final return being done twice because of the way the %NOTFOUND is handled by PL/SQL.

8. What are SQLCODE and SQLERRM and why are they important for PL/SQL developers?
Level: Intermediate
Expected answer: SQLCODE returns the value of the error number for the last error encountered. The SQLERRM returns the actual error message for the last error encountered. They can be used in exception handling to report, or, store in an error log table, the error that occurred in the code. These are especially useful for the WHEN OTHERS exception.

9. How can you find within a PL/SQL block, if a cursor is open?
Level: Low
Expected answer: Use the %ISOPEN cursor status variable.

10. How can you generate debugging output from PL/SQL?
Level:Intermediate to high
Expected answer: Use the DBMS_OUTPUT package. Another possible method is to just use the SHOW ERROR command, but this only shows errors. The DBMS_OUTPUT package can be used to show intermediate results from loops and the status of variables as the procedure is executed. The new package UTL_FILE can also be used.

11. What are the types of triggers?
Level:Intermediate to high
Expected Answer: There are 12 types of triggers in PL/SQL that consist of combinations of the BEFORE, AFTER, ROW, TABLE, INSERT, UPDATE, DELETE and ALL key words:
BEFORE ALL ROW INSERT
AFTER ALL ROW INSERT
BEFORE INSERT
AFTER INSERT etc.

DBA:
1. Give one method for transferring a table from one schema to another:
Level:Intermediate
Expected Answer: There are several possible methods, export-import, CREATE TABLE... AS SELECT, or COPY.

2. What is the purpose of the IMPORT option IGNORE? What is it?s default setting?
Level: Low
Expected Answer: The IMPORT IGNORE option tells import to ignore "already exists" errors. If it is not specified the tables that already exist will be skipped. If it is specified, the error is ignored and the tables data will be inserted. The default value is N.

3. You have a rollback segment in a version 7.2 database that has expanded beyond optimal, how can it be restored to optimal?
Level: Low
Expected answer: Use the ALTER TABLESPACE ..... SHRINK command.

4. If the DEFAULT and TEMPORARY tablespace clauses are left out of a CREATE USER command what happens? Is this bad or good? Why?
Level: Low
Expected answer: The user is assigned the SYSTEM tablespace as a default and temporary tablespace. This is bad because it causes user objects and temporary segments to be placed into the SYSTEM tablespace resulting in fragmentation and improper table placement (only data dictionary objects and the system rollback segment should be in SYSTEM).

5. What are some of the Oracle provided packages that DBAs should be aware of?
Level: Intermediate to High
Expected answer: Oracle provides a number of packages in the form of the DBMS_ packages owned by the SYS user. The packages used by DBAs may include: DBMS_SHARED_POOL, DBMS_UTILITY, DBMS_SQL, DBMS_DDL, DBMS_SESSION, DBMS_OUTPUT and DBMS_SNAPSHOT. They may also try to answer with the UTL*.SQL or CAT*.SQL series of SQL procedures. These can be viewed as extra credit but aren?t part of the answer.

6. What happens if the constraint name is left out of a constraint clause?
Level: Low
Expected answer: The Oracle system will use the default name of SYS_Cxxxx where xxxx is a system generated number. This is bad since it makes tracking which table the constraint belongs to or what the constraint does harder.

7. What happens if a tablespace clause is left off of a primary key constraint clause?
Level: Low
Expected answer: This results in the index that is automatically generated being placed in then users default tablespace. Since this will usually be the same tablespace as the table is being created in, this can cause serious performance problems.

8. What is the proper method for disabling and re-enabling a primary key constraint?
Level: Intermediate
Expected answer: You use the ALTER TABLE command for both. However, for the enable clause you must specify the USING INDEX and TABLESPACE clause for primary keys.

9. What happens if a primary key constraint is disabled and then enabled without fully specifying the index clause?
Level: Intermediate
Expected answer: The index is created in the user?s default tablespace and all sizing information is lost. Oracle doesn?t store this information as a part of the constraint definition, but only as part of the index definition, when the constraint was disabled the index was dropped and the information is gone.

10. (On UNIX) When should more than one DB writer process be used? How many should be used?
Level: High
Expected answer: If the UNIX system being used is capable of asynchronous IO then only one is required, if the system is not capable of asynchronous IO then up to twice the number of disks used by Oracle number of DB writers should be specified by use of the db_writers initialization parameter.

11. You are using hot backup without being in archivelog mode, can you recover in the event of a failure? Why or why not?
Level: High
Expected answer: You can?t use hot backup without being in archivelog mode. So no, you couldn?t recover.

12. What causes the "snapshot too old" error? How can this be prevented or mitigated?
Level: Intermediate
Expected answer: This is caused by large or long running transactions that have either wrapped onto their own rollback space or have had another transaction write on part of their rollback space. This can be prevented or mitigated by breaking the transaction into a set of smaller transactions or increasing the size of the rollback segments and their extents.

13. How can you tell if a database object is invalid?
Level: Low
Expected answer: By checking the status column of the DBA_, ALL_ or USER_OBJECTS views, depending upon whether you own or only have permission on the view or are using a DBA account.

14. A user is getting an ORA-00942 error yet you know you have granted them permission on the table, what else should you check?
Level: Low
Expected answer: You need to check that the user has specified the full name of the object (select empid from scott.emp; instead of select empid from emp;) or has a synonym that points to the object (create synonym emp for scott.emp;)

15. A developer is trying to create a view and the database won?t let him. He has the "DEVELOPER" role which has the "CREATE VIEW" system privilege and SELECT grants on the tables he is using, what is the problem?
Level: Intermediate
Expected answer: You need to verify the developer has direct grants on all tables used in the view. You can?t create a stored object with grants given through views.

16. If you have an example table, what is the best way to get sizing data for the production table implementation?
Level: Intermediate
Expected answer: The best way is to analyze the table and then use the data provided in the DBA_TABLES view to get the average row length and other pertinent data for the calculation. The quick and dirty way is to look at the number of blocks the table is actually using and ratio the number of rows in the table to its number of blocks against the number of expected rows.

17. How can you find out how many users are currently logged into the database? How can you find their operating system id?
Level: high
Expected answer: There are several ways. One is to look at the v$session or v$process views. Another way is to check the current_logins parameter in the v$sysstat view. Another if you are on UNIX is to do a "ps -efgrep oraclewc -l? command, but this only works against a single instance installation.

18. A user selects from a sequence and gets back two values, his select is:
SELECT pk_seq.nextval FROM dual;
What is the problem?
Level: Intermediate
Expected answer: Somehow two values have been inserted into the dual table. This table is a single row, single column table that should only have one value in it.

19. How can you determine if an index needs to be dropped and rebuilt?
Level: Intermediate
Expected answer: Run the ANALYZE INDEX command on the index to validate its structure and then calculate the ratio of LF_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN and if it isn?t near 1.0 (i.e. greater than 0.7 or so) then the index should be rebuilt. Or if the ratio
BR_BLK_LEN/ LF_BLK_LEN+BR_BLK_LEN is nearing 0.3.

SQL/ SQLPlus

1. How can variables be passed to a SQL routine?
Level: Low
Expected answer: By use of the & symbol. For passing in variables the numbers 1-8 can be used (&1, &2,...,&8) to pass the values after the command into the SQLPLUS session. To be prompted for a specific variable, place the ampersanded variable in the code itself:
"select * from dba_tables where owner=&owner_name;" . Use of double ampersands tells SQLPLUS to resubstitute the value for each subsequent use of the variable, a single ampersand will cause a reprompt for the value unless an ACCEPT statement is used to get the value from the user.

2. You want to include a carriage return/linefeed in your output from a SQL script, how can you do this?
Level: Intermediate to high
Expected answer: The best method is to use the CHR() function (CHR(10) is a return/linefeed) and the concatenation function "". Another method, although it is hard to document and isn?t always portable is to use the return/linefeed as a part of a quoted string.

3. How can you call a PL/SQL procedure from SQL?
Level: Intermediate
Expected answer: By use of the EXECUTE (short form EXEC) command.
4. How do you execute a host operating system command from within SQL?
Level: Low
Expected answer: By use of the exclamation point "!" (in UNIX and some other OS) or the HOST (HO) command.

5. You want to use SQL to build SQL, what is this called and give an example
Level: Intermediate to high
Expected answer: This is called dynamic SQL. An example would be:
set lines 90 pages 0 termout off feedback off verify off
spool drop_all.sql
select ?drop user ?username? cascade;? from dba_users
where username not in ("SYS?,?SYSTEM?);
spool off
Essentially you are looking to see that they know to include a command (in this case DROP USER...CASCADE;) and that you need to concatenate using the ?? the values selected from the database.

6. What SQLPlus command is used to format output from a select?
Level: low
Expected answer: This is best done with the COLUMN command.

7. You want to group the following set of select returns, what can you group on?
Max(sum_of_cost), min(sum_of_cost), count(item_no), item_no
Level: Intermediate
Expected answer: The only column that can be grouped on is the "item_no" column, the rest have aggregate functions associated with them.

8. What special Oracle feature allows you to specify how the cost based system treats a SQL statement?
Level: Intermediate to high
Expected answer: The COST based system allows the use of HINTs to control the optimizer path selection. If they can give some example hints such as FIRST ROWS, ALL ROWS, USING INDEX, STAR, even better.

9. You want to determine the location of identical rows in a table before attempting to place a unique index on the table, how can this be done?
Level: High
Expected answer: Oracle tables always have one guaranteed unique column, the rowid column. If you use a min/max function against your rowid and then select against the proposed primary key you can squeeze out the rowids of the duplicate rows pretty quick. For example:
select rowid from emp e
where e.rowid > (select min(x.rowid)
from emp x
where x.emp_no = e.emp_no);
In the situation where multiple columns make up the proposed key, they must all be used in the where clause.

10. What is a Cartesian product?
Level: Low
Expected answer: A Cartesian product is the result of an unrestricted join of two or more tables. The result set of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to the number of rows in each table involved in the join.

11. You are joining a local and a remote table, the network manager complains about the traffic involved, how can you reduce the network traffic?
Level: High
Expected answer: Push the processing of the remote data to the remote instance by using a view to pre-select the information for the join. This will result in only the data required for the join being sent across.

12. What is the default ordering of an ORDER BY clause in a SELECT statement?
Level: Low
Expected answer: Ascending

13. What is tkprof and how is it used?
Level: Intermediate to high
Expected answer: The tkprof tool is a tuning tool used to determine cpu and execution times for SQL statements. You use it by first setting timed_statistics to true in the initialization file and then turning on tracing for either the entire database via the sql_trace parameter or for the session using the ALTER SESSION command. Once the trace file is generated you run the tkprof tool against the trace file and then look at the output from the tkprof tool. This can also be used to generate explain plan output.

14. What is explain plan and how is it used?
Level: Intermediate to high
Expected answer: The EXPLAIN PLAN command is a tool to tune SQL statements. To use it you must have an explain_table generated in the user you are running the explain plan for. This is created using the utlxplan.sql script. Once the explain plan table exists you run the explain plan command giving as its argument the SQL statement to be explained. The explain_plan table is then queried to see the execution plan of the statement. Explain plans can also be run using tkprof.

15. How do you set the number of lines on a page of output? The width?
Level: Low
Expected answer: The SET command in SQLPLUS is used to control the number of lines generated per page and the width of those lines, for example SET PAGESIZE 60 LINESIZE 80 will generate reports that are 60 lines long with a line width of 80 characters. The PAGESIZE and LINESIZE options can be shortened to PAGES and LINES.

16. How do you prevent output from coming to the screen?
Level: Low
Expected answer: The SET option TERMOUT controls output to the screen. Setting TERMOUT OFF turns off screen output. This option can be shortened to TERM.

17. How do you prevent Oracle from giving you informational messages during and after a SQL statement execution?
Level: Low
Expected answer: The SET options FEEDBACK and VERIFY can be set to OFF.

18. How do you generate file output from SQL?
Level: Low
Expected answer: By use of the SPOOL command

Tuning Questions:
1. A tablespace has a table with 30 extents in it. Is this bad? Why or why not.
Level: Intermediate
Expected answer: Multiple extents in and of themselves aren?t bad. However if you also have chained rows this can hurt performance.

2. How do you set up tablespaces during an Oracle installation?
Level: Low
Expected answer: You should always attempt to use the Oracle Flexible Architecture standard or another partitioning scheme to ensure proper separation of SYSTEM, ROLLBACK, REDO LOG, DATA, TEMPORARY and INDEX segments.

3. You see multiple fragments in the SYSTEM tablespace, what should you check first?
Level: Low
Expected answer: Ensure that users don?t have the SYSTEM tablespace as their TEMPORARY or DEFAULT tablespace assignment by checking the DBA_USERS view.

4. What are some indications that you need to increase the SHARED_POOL_SIZE parameter?
Level: Intermediate
Expected answer: Poor data dictionary or library cache hit ratios, getting error ORA-04031. Another indication is steadily decreasing performance with all other tuning parameters the same.

5. What is the general guideline for sizing db_block_size and db_multi_block_read for an application that does many full table scans?
Level: High
Expected answer: Oracle almost always reads in 64k chunks. The two should have a product equal to 64 or a multiple of 64.

6. What is the fastest query method for a table?
Level: Intermediate
Expected answer: Fetch by rowid

7. Explain the use of TKPROF? What initialization parameter should be turned on to get full TKPROF output?
Level: High
Expected answer: The tkprof tool is a tuning tool used to determine cpu and execution times for SQL statements. You use it by first setting timed_statistics to true in the initialization file and then turning on tracing for either the entire database via the sql_trace parameter or for the session using the ALTER SESSION command. Once the trace file is generated you run the tkprof tool against the trace file and then look at the output from the tkprof tool. This can also be used to generate explain plan output.

8. When looking at v$sysstat you see that sorts (disk) is high. Is this bad or good? If bad -How do you correct it?
Level: Intermediate
Expected answer: If you get excessive disk sorts this is bad. This indicates you need to tune the sort area parameters in the initialization files. The major sort are parameter is the SORT_AREA_SIZe parameter.

9. When should you increase copy latches? What parameters control copy latches?
Level: high
Expected answer: When you get excessive contention for the copy latches as shown by the "redo copy" latch hit ratio. You can increase copy latches via the initialization parameter LOG_SIMULTANEOUS_COPIES to twice the number of CPUs on your system.

10. Where can you get a list of all initialization parameters for your instance? How about an indication if they are default settings or have been changed?
Level: Low
Expected answer: You can look in the init.ora file for an indication of manually set parameters. For all parameters, their value and whether or not the current value is the default value, look in the v$parameter view.

11. Describe hit ratio as it pertains to the database buffers. What is the difference between instantaneous and cumulative hit ratio and which should be used for tuning?
Level: Intermediate
Expected answer: The hit ratio is a measure of how many times the database was able to read a value from the buffers verses how many times it had to re-read a data value from the disks. A value greater than 80-90% is good, less could indicate problems. If you simply take the ratio of existing parameters this will be a cumulative value since the database started. If you do a comparison between pairs of readings based on some arbitrary time span, this is the instantaneous ratio for that time span. Generally speaking an instantaneous reading gives more valuable data since it will tell you what your instance is doing for the time it was generated over.

12. Discuss row chaining, how does it happen? How can you reduce it? How do you correct it?
Level: high
Expected answer: Row chaining occurs when a VARCHAR2 value is updated and the length of the new value is longer than the old value and won?t fit in the remaining block space. This results in the row chaining to another block. It can be reduced by setting the storage parameters on the table to appropriate values. It can be corrected by export and import of the effected table.

13. When looking at the estat events report you see that you are getting busy buffer waits. Is this bad? How can you find what is causing it?
Level: high
Expected answer: Buffer busy waits could indicate contention in redo, rollback or data blocks. You need to check the v$waitstat view to see what areas are causing the problem. The value of the "count" column tells where the problem is, the "class" column tells you with what. UNDO is rollback segments, DATA is data base buffers.

14. If you see contention for library caches how can you fix it?
Level: Intermediate
Expected answer: Increase the size of the shared pool.

15. If you see statistics that deal with "undo" what are they really talking about?
Level: Intermediate
Expected answer: Rollback segments and associated structures.

16. If a tablespace has a default pctincrease of zero what will this cause (in relationship to the smon process)?
Level: High
Expected answer: The SMON process won?t automatically coalesce its free space fragments.

17. If a tablespace shows excessive fragmentation what are some methods to defragment the tablespace? (7.1,7.2 and 7.3 only)
Level: High
Expected answer: In Oracle 7.0 to 7.2 The use of the 'alter session set events 'immediate trace name coalesce level ts#';? command is the easiest way to defragment contiguous free space fragmentation. The ts# parameter corresponds to the ts# value found in the ts$ SYS table. In version 7.3 the ?alter tablespace coalesce;? is best. If the free space isn?t contiguous then export, drop and import of the tablespace contents may be the only way to reclaim non-contiguous free space.

18. How can you tell if a tablespace has excessive fragmentation?
Level: Intermediate
If a select against the dba_free_space table shows that the count of a tablespaces extents is greater than the count of its data files, then it is fragmented.

19. You see the following on a status report:
redo log space requests 23
redo log space wait time 0
Is this something to worry about? What if redo log space wait time is high? How can you fix this? Level: Intermediate
Expected answer: Since the wait time is zero, no. If the wait time was high it might indicate a need for more or larger redo logs.

20. What can cause a high value for recursive calls? How can this be fixed?
Level: High
Expected answer: A high value for recursive calls is cause by improper cursor usage, excessive dynamic space management actions, and or excessive statement re-parses. You need to determine the cause and correct it By either relinking applications to hold cursors, use proper space management techniques (proper storage and sizing) or ensure repeat queries are placed in packages for proper reuse.

21. If you see a pin hit ratio of less than 0.8 in the estat library cache report is this a problem? If so, how do you fix it?
Level: Intermediate
Expected answer: This indicate that the shared pool may be too small. Increase the shared pool size.

22. If you see the value for reloads is high in the estat library cache report is this a matter for concern?
Level: Intermediate
Expected answer: Yes, you should strive for zero reloads if possible. If you see excessive reloads then increase the size of the shared pool.

23. You look at the dba_rollback_segs view and see that there is a large number of shrinks and they are of relatively small size, is this a problem? How can it be fixed if it is a problem?
Level: High
Expected answer: A large number of small shrinks indicates a need to increase the size of the rollback segment extents. Ideally you should have no shrinks or a small number of large shrinks. To fix this just increase the size of the extents and adjust optimal accordingly.

24. You look at the dba_rollback_segs view and see that you have a large number of wraps is this a problem?
Level: High
Expected answer: A large number of wraps indicates that your extent size for your rollback segments are probably too small. Increase the size of your extents to reduce the number of wraps. You can look at the average transaction size in the same view to get the information on transaction size.

25. In a system with an average of 40 concurrent users you get the following from a query on rollback extents:
ROLLBACK CUR EXTENTS
--------------------- --------------------------
R01 11
R02 8
R03 12
R04 9
SYSTEM 4
You have room for each to grow by 20 more extents each. Is there a problem? Should you take any action?
Level: Intermediate
Expected answer: No there is not a problem. You have 40 extents showing and an average of 40 concurrent users. Since there is plenty of room to grow no action is needed.

26. You see multiple extents in the temporary tablespace. Is this a problem?
Level: Intermediate
Expected answer: As long as they are all the same size this isn?t a problem. In fact, it can even improve performance since Oracle won?t have to create a new extent when a user needs one.

Installation/Configuration
1. Define OFA.
Level: Low
Expected answer: OFA stands for Optimal Flexible Architecture. It is a method of placing directories and files in an Oracle system so that you get the maximum flexibility for future tuning and file placement.

2. How do you set up your tablespace on installation?
Level: Low
Expected answer: The answer here should show an understanding of separation of redo and rollback, data and indexes and isolation os SYSTEM tables from other tables. An example would be to specify that at least 7 disks should be used for an Oracle installation so that you can place SYSTEM tablespace on one, redo logs on two (mirrored redo logs) the TEMPORARY tablespace on another, ROLLBACK tablespace on another and still have two for DATA and INDEXES. They should indicate how they will handle archive logs and exports as well. As long as they have a logical plan for combining or further separation more or less disks can be specified.

3. What should be done prior to installing Oracle (for the OS and the disks)?
Level: Low
Expected Answer: adjust kernel parameters or OS tuning parameters in accordance with installation guide. Be sure enough contiguous disk space is available.

4. You have installed Oracle and you are now setting up the actual instance. You have been waiting an hour for the initialization script to finish, what should you check first to determine if there is a problem?
Level: Intermediate to high
Expected Answer: Check to make sure that the archiver isn?t stuck. If archive logging is turned on during install a large number of logs will be created. This can fill up your archive log destination causing Oracle to stop to wait for more space.

5. When configuring SQLNET on the server what files must be set up?
Level: Intermediate
Expected answer: INITIALIZATION file, TNSNAMES.ORA file, SQLNET.ORA file

6. When configuring SQLNET on the client what files need to be set up?
Level: Intermediate
Expected answer: SQLNET.ORA, TNSNAMES.ORA

7. What must be installed with ODBC on the client in order for it to work with Oracle?
Level: Intermediate
Expected answer: SQLNET and PROTOCOL (for example: TCPIP adapter) layers of the transport programs.

8. You have just started a new instance with a large SGA on a busy existing server. Performance is terrible, what should you check for?
Level: Intermediate
Expected answer: The first thing to check with a large SGA is that it isn?t being swapped out.

9. What OS user should be used for the first part of an Oracle installation (on UNIX)?
Level: low
Expected answer: You must use root first.

10. When should the default values for Oracle initialization parameters be used as is?
Level: Low
Expected answer: Never

11. How many control files should you have? Where should they be located?
Level: Low
Expected answer: At least 2 on separate disk spindles. Be sure they say on separate disks, not just file systems.

12. How many redo logs should you have and how should they be configured for maximum recoverability?
Level: Intermediate
Expected answer: You should have at least three groups of two redo logs with the two logs each on a separate disk spindle (mirrored by Oracle). The redo logs should not be on raw devices on UNIX if it can be avoided.

13. You have a simple application with no "hot" tables (i.e. uniform IO and access requirements). How many disks should you have assuming standard layout for SYSTEM, USER, TEMP and ROLLBACK tablespaces?
Expected answer: At least 7, see disk configuration answer above.

Data Modeler:
1. Describe third normal form?
Level: Low
Expected answer: Something like: In third normal form all attributes in an entity are related to the primary key and only to the primary key

2. Is the following statement true or false:
"All relational databases must be in third normal form"
Why or why not?
Level: Intermediate
Expected answer: False. While 3NF is good for logical design most databases, if they have more than just a few tables, will not perform well using full 3NF. Usually some entities will be denormalized in the logical to physical transfer process.

3. What is an ERD?
Level: Low
Expected answer: An ERD is an Entity-Relationship-Diagram. It is used to show the entities and relationships for a database logical model.

4. Why are recursive relationships bad? How do you resolve them?
Level: Intermediate
A recursive relationship (one where a table relates to itself) is bad when it is a hard relationship (i.e. neither side is a "may" both are "must") as this can result in it not being possible to put in a top or perhaps a bottom of the table (for example in the EMPLOYEE table you couldn?t put in the PRESIDENT of the company because he has no boss, or the junior janitor because he has no subordinates). These type of relationships are usually resolved by adding a small intersection entity.

5. What does a hard one-to-one relationship mean (one where the relationship on both ends is "must")?
Level: Low to intermediate
Expected answer: This means the two entities should probably be made into one entity.

6. How should a many-to-many relationship be handled?
Level: Intermediate
Expected answer: By adding an intersection entity table

7. What is an artificial (derived) primary key? When should an artificial (or derived) primary key be used?
Level: Intermediate
Expected answer: A derived key comes from a sequence. Usually it is used when a concatenated key becomes too cumbersome to use as a foreign key.

8. When should you consider denormalization?
Level: Intermediate
Expected answer: Whenever performance analysis indicates it would be beneficial to do so without compromising data integrity.

UNIX:
1. How can you determine the space left in a file system?
Level: Low
Expected answer: There are several commands to do this: du, df, or bdf

2. How can you determine the number of SQLNET users logged in to the UNIX system?
Level: Intermediate
Expected answer: SQLNET users will show up with a process unique name that begins with oracle, if you do a ps -efgrep oraclewc -l you can get a count of the number of users.

3. What command is used to type files to the screen?
Level: Low
Expected answer: cat, more, pg

4. What command is used to remove a file?
Level: Low
Expected answer: rm

5. Can you remove an open file under UNIX?
Level: Low
Expected answer: yes

6. How do you create a decision tree in a shell script?
Level: intermediate
Expected answer: depending on shell, usually a case-esac or an if-endif or fi structure

7. What is the purpose of the grep command?
Level: Low
Expected answer: grep is a string search command that parses the specified string from the specified file or files

8. The system has a program that always includes the word nocomp in its name, how can you determine the number of processes that are using this program?
Level: intermediate
Expected answer: ps -efgrep *nocomp*wc -l

9. What is an inode?
Level: Intermediate
Expected answer: an inode is a file status indicator. It is stored in both disk and memory and tracts file status. There is one inode for each file on the system.

10. The system administrator tells you that the system hasn?t been rebooted in 6 months, should he be proud of this?
Level: High
Expected answer: Maybe. Some UNIX systems don?t clean up well after themselves. Inode problems and dead user processes can accumulate causing possible performance and corruption problems. Most UNIX systems should have a scheduled periodic reboot so file systems can be checked and cleaned and dead or zombie processes cleared out.

11. What is redirection and how is it used?
Level: Intermediate
Expected answer: redirection is the process by which input or output to or from a process is redirected to another process. This can be done using the pipe symbol "", the greater than symbol ">" or the "tee" command. This is one of the strengths of UNIX allowing the output from one command to be redirected directly into the input of another command.

12. How can you find dead processes?
Level: Intermediate
Expected answer: ps -efgrep zombie -- or -- who -d depending on the system.

13. How can you find all the processes on your system?
Level: Low
Expected answer: Use the ps command

14. How can you find your id on a system?
Level: Low
Expected answer: Use the "who am i" command.

15. What is the finger command?
Level: Low
Expected answer: The finger command uses data in the passwd file to give information on system users.

16. What is the easiest method to create a file on UNIX?
Level: Low
Expected answer: Use the touch command

17. What does >> do?
Level: Intermediate
Expected answer: The ">>" redirection symbol appends the output from the command specified into the file specified. The file must already have been created.

18. If you aren?t sure what command does a particular UNIX function what is the best way to determine the command?
Expected answer: The UNIX man -k command will search the man pages for the value specified. Review the results from the command to find the command of interest.

Oracle Troubleshooting:
1. How can you determine if an Oracle instance is up from the operating system level?
Level: Low
Expected answer: There are several base Oracle processes that will be running on multi-user operating systems, these will be smon, pmon, dbwr and lgwr. Any answer that has them using their operating system process showing feature to check for these is acceptable. For example, on UNIX a ps -efgrep dbwr will show what instances are up.

2. Users from the PC clients are getting messages indicating :
Level: Low
ORA-06114: (Cnct err, can't get err txt. See Servr Msgs & Codes Manual)
What could the problem be?
Expected answer: The instance name is probably incorrect in their connection string.

3. Users from the PC clients are getting the following error stack:
Level: Low
ERROR: ORA-01034: ORACLE not available
ORA-07318: smsget: open error when opening sgadef.dbf file.
HP-UX Error: 2: No such file or directory
What is the probable cause?
Expected answer: The Oracle instance is shutdown that they are trying to access, restart the instance.

4. How can you determine if the SQLNET process is running for SQLNET V1? How about V2?
Level: Low
Expected answer: For SQLNET V1 check for the existence of the orasrv process. You can use the command "tcpctl status" to get a full status of the V1 TCPIP server, other protocols have similar command formats. For SQLNET V2 check for the presence of the LISTENER process(s) or you can issue the command "lsnrctl status".

5. What file will give you Oracle instance status information? Where is it located?
Level: Low
Expected answer: The alert.ora log. It is located in the directory specified by the background_dump_dest parameter in the v$parameter table.

6. Users aren?t being allowed on the system. The following message is received:
Level: Intermediate
ORA-00257 archiver is stuck. Connect internal only, until freed
What is the problem?
Expected answer: The archive destination is probably full, backup the archive logs and remove them and the archiver will re-start.

7. Where would you look to find out if a redo log was corrupted assuming you are using Oracle mirrored redo logs?
Level: Intermediate
Expected answer: There is no message that comes to the SQLDBA or SRVMGR programs during startup in this situation, you must check the alert.log file for this information.

8. You attempt to add a datafile and get:
Level: Intermediate
ORA-01118: cannot add anymore datafiles: limit of 40 exceeded
What is the problem and how can you fix it?
Expected answer: When the database was created the db_files parameter in the initialization file was set to 40. You can shutdown and reset this to a higher value, up to the value of MAX_DATAFILES as specified at database creation. If the MAX_DATAFILES is set to low, you will have to rebuild the control file to increase it before proceeding.

9. You look at your fragmentation report and see that smon hasn?t coalesced any of you tablespaces, even though you know several have large chunks of contiguous free extents. What is the problem?
Level: High
Expected answer: Check the dba_tablespaces view for the value of pct_increase for the tablespaces. If pct_increase is zero, smon will not coalesce their free space.

10. Your users get the following error:
Level: Intermediate
ORA-00055 maximum number of DML locks exceeded
What is the problem and how do you fix it?
Expected answer: The number of DML Locks is set by the initialization parameter DML_LOCKS. If this value is set to low (which it is by default) you will get this error. Increase the value of DML_LOCKS. If you are sure that this is just a temporary problem, you can have them wait and then try again later and the error should clear.

11. You get a call from you backup DBA while you are on vacation. He has corrupted all of the control files while playing with the ALTER DATABASE BACKUP CONTROLFILE command. What do you do?
Level: High
Expected answer: As long as all datafiles are safe and he was successful with the BACKUP controlfile command you can do the following:
CONNECT INTERNAL
STARTUP MOUNT
(Take any read-only tablespaces offline before next step ALTER DATABASE DATAFILE .... OFFLINE;)
RECOVER DATABASE USING BACKUP CONTROLFILE
ALTER DATABASE OPEN RESETLOGS;
(bring read-only tablespaces back online)
Shutdown and backup the system, then restart
If they have a recent output file from the ALTER DATABASE BACKUP CONTROL FILE TO TRACE; command, they can use that to recover as well.
If no backup of the control file is available then the following will be required:
CONNECT INTERNAL
STARTUP NOMOUNT
CREATE CONTROL FILE .....;
However, they will need to know all of the datafiles, logfiles, and settings for MAXLOGFILES, MAXLOGMEMBERS, MAXLOGHISTORY, MAXDATAFILES for the database to use the command.

Reference: http://www.kanbal.com/index.php?/Database/dba-interview-questions-set-2.html
- by kannan

What is Log Switch? -
The point at which ORACLE ends writing to one online redo log file and begins writing to another is called a log switch.

What is On-line Redo Log?
The On-line Redo Log is a set of tow or more on-line redo files that record all committed changes made to the database. Whenever a transaction is committed, the corresponding redo entries temporarily stores in redo log buffers of the SGA are written to an on-line redo log file by the background process LGWR. The on-line redo log files are used in cyclical fashion.

Which parameter specified in the DEFAULT STORAGE clause of CREATE TABLESPACE cannot be altered after creating the tablespace? -
All the default storage parameters defined for the tablespace can be changed using the ALTER TABLESPACE command. When objects are created their INITIAL and MINEXTENS values cannot be changed.

What are the steps involved in Database Startup? - Start an instance, Mount the Database and Open the Database.

What are the steps involved in Instance Recovery? - Rolling forward to recover data that has not been recorded in data files, yet has been recorded in the on-line redo log, including the contents of rollback segments. Rolling back transactions that have been explicitly rolled back or have not been committed as indicated by the rollback segments regenerated in step a. Releasing any resources (locks) held by transactions in process at the time of the failure. Resolving any pending distributed transactions undergoing a two-phase commit at the time of the instance failure.

Can Full Backup be performed when the database is open? - No.

What are the different modes of mounting a Database with the Parallel Server? - Exclusive Mode If the first instance that mounts a database does so in exclusive mode, only that Instance can mount the database. Parallel Mode If the first instance that mounts a database is started in parallel mode, other instances that are started in parallel mode can also mount the database.

What are the advantages of operating a database in ARCHIVELOG mode over operating it in NO ARCHIVELOG mode? - Complete database recovery from disk failure is possible only in ARCHIVELOG mode. Online database backup is possible only in ARCHIVELOG mode.

What are the steps involved in Database Shutdown? - Close the Database, Dismount the Database and Shutdown the Instance.

What is Archived Redo Log? - Archived Redo Log consists of Redo Log files that have archived before being reused.

What is Restricted Mode of Instance Startup? - An instance can be started in (or later altered to be in) restricted mode so that when the database is open connections are limited only to those whose user accounts have been granted the RESTRICTED SESSION system privilege.

What is Partial Backup? - A Partial Backup is any operating system backup short of a full backup, taken while the database is open or shut down.

What is Mirrored on-line Redo Log? - A mirrored on-line redo log consists of copies of on-line redo log files physically located on separate disks, changes made to one member of the group are made to all members.

What is Full Backup? - A full backup is an operating system backup of all data files, on- line redo log files and control file that constitute ORACLE database and the parameter.

Can a View based on another View? - Yes.

Can a Tablespace hold objects from different Schemes? - Yes.

Can objects of the same Schema reside in different tablespaces? - Yes.

What is the use of Control File? - When an instance of an ORACLE database is started, its control file is used to identify the database and redo log files that must be opened for database operation to proceed. It is also used in database recovery.

Do View contain Data? - Views do not contain or store data.

What are the Referential actions supported by FOREIGN KEY integrity constraint? - UPDATE and DELETE Restrict - A referential integrity rule that disallows the update or deletion of referenced data. DELETE Cascade - When a referenced row is deleted all associated dependent rows are deleted.

What are the type of Synonyms? - There are two types of Synonyms Private and Public

What is a Redo Log? - The set of Redo Log files YSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.

What is an Index Segment? - Each Index has an Index segment that stores all of its data.

Explain the relationship among Database, Tablespace and Data file.? - Each databases logically divided into one or more tablespaces one or more data files are explicitly created for each tablespace

What are the different type of Segments? - Data Segment, Index Segment, Rollback Segment and Temporary Segment.

What are Clusters? - Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

What is an Integrity Constrains? - An integrity constraint is a declarative way to define a business rule for a column of a table.

What is an Index? - An Index is an optional structure associated with a table to have direct access to rows, which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

What is an Extent? - An Extent is a specific number of contiguous data blocks, obtained in a single allocation, and used to store a specific type of information.

What is a View? - A view is a virtual table. Every view has a Query attached to it. (The Query is a SELECT statement that identifies the columns and rows of the table(s) the view uses.)

What is Table? - A table is the basic unit of data storage in an ORACLE database. The tables of a database hold all of the user accessible data. Table data is stored in rows and columns.

What is a Synonym? - A synonym is an alias for a table, view, sequence or program unit.

What is a Sequence? - A sequence generates a serial list of unique numbers for numerical columns of a database’s tables.

What is a Segment? - A segment is a set of extents allocated for a certain logical structure.

What is schema? - A schema is collection of database objects of a User.

Describe Referential Integrity? - A rule defined on a column (or set of columns) in one table that allows the insert or update of a row only if the value for the column or set of columns (the dependent value) matches a value in a column of a related table (the referenced value). It also specifies the type of data manipulation allowed on referenced data and the action to be performed on dependent data as a result of any action on referenced data.

What is Hash Cluster? - A row is stored in a hash cluster based on the result of applying a hash function to the row’s cluster key value. All rows with the same hash key value are stores together on disk.

What is a Private Synonyms? - A Private Synonyms can be accessed only by the owner.

What is Database Link? - A database link is a named object that describes a “path” from one database to another.

What is a Tablespace? - A database is divided into Logical Storage Unit called tablespaces. A tablespace is used to grouped related logical structures together

What is Rollback Segment? - A Database contains one or more Rollback Segments to temporarily store “undo” information.

What are the Characteristics of Data Files? - A data file can be associated with only one database. Once created a data file can’t change size. One or more data files form a logical unit of database storage called a tablespace.

How to define Data Block size? - A data block size is specified for each ORACLE database when the database is created. A database users and allocated free database space in ORACLE datablocks. Block size is specified in INIT.ORA file and can’t be changed latter.

What does a Control file Contain? - A Control file records the physical structure of the database. It contains the following information. Database Name Names and locations of a database’s files and redolog files. Time stamp of database creation.

What is difference between UNIQUE constraint and PRIMARY KEY constraint? - A column defined as UNIQUE can contain Nulls while a column defined as PRIMARY KEY can’t contain Nulls.

What is Index Cluster? - A Cluster with an index on the Cluster Key

When does a Transaction end? - When it is committed or Rollbacked.

What is the effect of setting the value “ALL_ROWS” for OPTIMIZER_GOAL parameter of the ALTER SESSION command? - What are the factors that affect OPTIMIZER in choosing an Optimization approach? - Answer The OPTIMIZER_MODE initialization parameter Statistics in the Data Dictionary the OPTIMIZER_GOAL parameter of the ALTER SESSION command hints in the statement.

What is the effect of setting the value “CHOOSE” for OPTIMIZER_GOAL, parameter of the ALTER SESSION Command? - The Optimizer chooses Cost_based approach and optimizes with the goal of best throughput if statistics for atleast one of the tables accessed by the SQL statement exist in the data dictionary. Otherwise the OPTIMIZER chooses RULE_based approach.

What is the function of Optimizer? - The goal of the optimizer is to choose the most efficient way to execute a SQL statement.

What is Execution Plan? - The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.

What are the different approaches used by Optimizer in choosing an execution plan? - Rule-based and Cost-based.

What does ROLLBACK do? - ROLLBACK retracts any of the changes resulting from the SQL statements in the transaction.

What is SAVE POINT? - For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can be used to divide a transaction into smaller parts. This allows the option of later rolling back all work performed from the current point in the transaction to a declared savepoint within the transaction.

What are the values that can be specified for OPTIMIZER MODE Parameter? - Cost and RULE.

What is COST-based approach to optimization? - Considering available access paths and determining the most efficient execution plan based on statistics in the data dictionary for the tables accessed by the statement and their associated clusters and indexes.

What does COMMIT do? - COMMIT makes permanent the changes resulting from all SQL statements in the transaction. The changes made by the SQL statements of a transaction become visible to other user sessions transactions that start only after transaction is committed.

What is RULE-based approach to optimization? - Choosing an executing plan based on the access paths available and the ranks of these access paths.

What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command? - CHOOSE,ALL_ROWS,FIRST_ROWS and RULE.

Define Transaction? - A Transaction is a logical unit of work that comprises one or more SQL statements executed by a single user.

What is Read-Only Transaction? - A Read-Only transaction ensures that the results of each query executed in the transaction are consistent with respect to the same point in time.

What is a deadlock? - Explain . Two processes waiting to update the rows of a table which are locked by the other process then deadlock arises. In a database environment this will often happen because of not issuing proper row lock commands. Poor design of front-end application may cause this situation and the performance of server will reduce drastically. These locks will be released automatically when a commit/rollback operation performed or any one of this processes being killed externally.

What is a Schema? - The set of objects owned by user account is called the schema.

What is a cluster Key? - The related columns of the tables are called the cluster key. The cluster key is indexed using a cluster index and its value is stored only once for multiple tables in the cluster.

What is Parallel Server? - Multiple instances accessing the same database (Only In Multi-CPU environments)

What are the basic element of Base configuration of an oracle Database? - It consists of one or more data files. one or more control files. two or more redo log files. The Database contains multiple users/schemas one or more rollback segments one or more tablespaces Data dictionary tables User objects (table, indexes, views etc.,) The server that access the database consists of SGA (Database buffer, Dictionary Cache Buffers, Redo log buffers, Shared SQL pool) SMON (System MONito) PMON (Process MONitor) LGWR (LoG Write) DBWR (Data Base Write) ARCH (ARCHiver) CKPT (Check Point) RECO Dispatcher User Process with associated PGS

What is clusters? - Group of tables physically stored together because they share common columns and are often used together is called Cluster.

What is an Index? - How it is implemented in Oracle Database? - An index is a database structure used by the server to have direct access of a row in a table. An index is automatically created when a unique of primary key constraint clause is specified in create table command (Ver 7.0)

What is a Database instance? - Explain A database instance (Server) is a set of memory structure and background processes that access a set of database files. The process can be shared by all users. The memory structure that are used to store most queried data from database. This helps up to improve database performance by decreasing the amount of I/O performed against data file.

What is the use of ANALYZE command? - To perform one of these function on an index, table, or cluster: - To collect statistics about object used by the optimizer and store them in the data dictionary. - To delete statistics about the object used by object from the data dictionary. - To validate the structure of the object.. - To identify migrated and chained rows off the table or cluster.

What is default tablespace? - The Tablespace to contain schema objects created without specifying a tablespace name.

What are the system resources that can be controlled through Profile? - The number of concurrent sessions the user can establish the CPU processing time available to the user’s session the CPU processing time available to a single call to ORACLE made by a SQL statement the amount of logical I/O available to the user’s session the amount of logical I/O available to a single call to ORACLE made by a SQL statement the allowed amount of idle time for the user’s session the allowed amount of connect time for the user’s session.

What is Tablespace Quota? - The collective amount of disk space available to the objects in a schema on a particular tablespace.

What are the different Levels of Auditing? - Statement Auditing, Privilege Auditing and Object Auditing.

What is Statement Auditing? - Statement auditing is the auditing of the powerful system privileges without regard to specifically named objects

What are the database administrators utilities available? - SQL * DBA - This allows DBA to monitor and control an ORACLE database. SQL * Loader - It loads data from standard operating system files (Flat files) into ORACLE database tables. Export (EXP) and Import (imp) utilities allow you to move existing data in ORACLE format to and from ORACLE database.

How can you enable automatic archiving? - Shut the database Backup the database Modify/Include LOG_ARCHIVE_START_TRUE in init.ora file. Start up the database.

What are roles? - How can we implement roles? - Roles are the easiest way to grant and manage common privileges needed by different groups of database users. Creating roles and assigning provides to roles. Assign each role to group of users. This will simplify the job of assigning privileges to individual users.

What are Roles? - Roles are named groups of related privileges that are granted to users or other roles.

What are the use of Roles? - REDUCED GRANTING OF PRIVILEGES - Rather than explicitly granting the same set of privileges to many users a database administrator can grant the privileges for a group of related users granted to a role and then grant only the role to each member of the group. DYNAMIC PRIVILEGE MANAGEMENT - When the privileges of a group must change, only the privileges of the role need to be modified. The security domains of all users granted the group’s role automatically reflect the changes made to the role. SELECTIVE AVAILABILITY OF PRIVILEGES - The roles granted to a user can be selectively enable (available for use) or disabled (not available for use). This allows specific control of a user’s privileges in any given situation. APPLICATION AWARENESS - A database application can be designed to automatically enable and disable selective roles when a user attempts to use the application.

What is Privilege Auditing? - Privilege auditing is the auditing of the use of powerful system privileges without regard to specifically named objects.

What is Object Auditing? - Object auditing is the auditing of accesses to specific schema objects without regard to user.

What is Auditing? - Monitoring of user access to aid in the investigation of database use.

What are the responsibilities of a Database Administrator?
Installing and upgrading the Oracle Server and application tools.
Allocating system storage and planning future storage requirements for the database system.
Managing primary database structures (tablespaces)
Managing primary objects (table, views, indexes)
Enrolling users and maintaining system security.
Ensuring compliance with Oracle license agreement
Controlling and monitoring user access to the database.
Monitoring and optimizing the performance of the database.
Planning for backup and recovery of database information.
Maintain archived data on tape
Backing up and restoring the database.
Contacting Oracle Corporation for technical support.

What is a trace file and how is it created? - Each server and background process can write an associated trace file. When an internal error is detected by a process or user process, it dumps information about the error to its trace. This can be used for tuning the database.

What is a profile? - Each database user is assigned a Profile that specifies limitations on various system resources available to the user.

How will you enforce security using stored procedures? - Don’t grant user access directly to tables within the application. Instead grant the ability to access the procedures that access the tables. When procedure executed it will execute the privilege of procedures owner. Users cannot access tables except via the procedure.

What are the dictionary tables used to monitor a database spaces? - DBA_FREE_SPACE DBA_SEGMENTS DBA_DATA_FILES.

What are the roles and user accounts created automatically with the database? - DBA - role Contains all database system privileges. SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database’s dictionary are store in this schema and are manipulated only by ORACLE. SYSTEM user account - It has all the system privileges for the database and additional tables and views that display administrative information and internal tables and views used by oracle tools are created using this username.

What are the minimum parameters should exist in the parameter file (init.ora)? - DB NAME - Must set to a text string of no more than 8 characters and it will be stored inside the datafiles, redo log files and control files and control file while database creation. DB_DOMAIN - It is string that specifies the network domain where the database is created. The global database name is identified by setting these parameters (DB_NAME & DB_DOMAIN) CONTORL FILES - List of control filenames of the database. If name is not mentioned then default name will be used. DB_BLOCK_BUFFERS - To determine the no of buffers in the buffer cache in SGA. PROCESSES - To determine number of operating system processes that can be connected to ORACLE concurrently. The value should be 5 (background process) and additional 1 for each user. ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance acquires at database startup. Also optionally LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.

How can we specify the Archived log file name format and destination? - By setting the following values in init.ora file. LOG_ARCHIVE_FORMAT = arch %S/s/T/tarc (%S - Log sequence number and is zero left padded, %s - Log sequence number not padded. %T - Thread number left-zero- padded and %t - Thread number not padded). The file name created is arch 0001 are if %S is used. LOG_ARCHIVE_DEST = path.

What is user Account in Oracle database? - An user account is not a physical structure in Database but it is having important relationship to the objects in the database and will be having certain privileges. 95.

When will the data in the snapshot log be used? - We must be able to create a after row trigger on table (i.e., it should be not be already available) After giving table privileges. We cannot specify snapshot log name because oracle uses the name of the master table in the name of the database objects that support its snapshot log. The master table name should be less than or equal to 23 characters. (The table name created will be MLOGS_tablename, and trigger name will be TLOGS name).

What dynamic data replication? - Updating or Inserting records in remote database through database triggers. It may fail if remote database is having any problem.

What is Two-Phase Commit? - Two-phase commit is mechanism that guarantees a distributed transaction either commits on all involved nodes or rolls back on all involved nodes to maintain data consistency across the global distributed database. It has two phase, a Prepare Phase and a Commit Phase.

How can you Enforce Referential Integrity in snapshots? - Time the references to occur when master tables are not in use. Peform the reference the manually immdiately locking the master tables. We can join tables in snopshots by creating a complex snapshots that will based on the master tables.

What is a SQL * NET? - SQL *NET is ORACLE’s mechanism for interfacing with the communication protocols used by the networks that facilitate distributed processing and distributed databases. It is used in Clint-Server and Server-Server communications.

What is a SNAPSHOT? - Snapshots are read-only copies of a master table located on a remote node which is periodically refreshed to reflect changes made to the master table.

What is the mechanism provided by ORACLE for table replication? - Snapshots and SNAPSHOT LOGs

What is snapshots? - Snapshot is an object used to dynamically replicate data between distribute database at specified time intervals. In ver 7.0 they are read only.

What are the various type of snapshots? - Simple and Complex.

Describe two phases of Two-phase commit? - Prepare phase - The global coordinator (initiating node) ask a participants to prepare (to promise to commit or rollback the transaction, even if there is a failure) Commit - Phase - If all participants respond to the coordinator that they are prepared, the coordinator asks all nodes to commit the transaction, if all participants cannot prepare, the coordinator asks all nodes to roll back the transaction.

What is snapshot log? - It is a table that maintains a record of modifications to the master table in a snapshot. It is stored in the same database as master table and is only available for simple snapshots. It should be created before creating snapshots.

What are the benefits of distributed options in databases? - Database on other servers can be updated and those transactions can be grouped together with others in a logical unit. Database uses a two phase commit.

What are the options available to refresh snapshots? - COMPLETE - Tables are completely regenerated using the snapshots query and the master tables every time the snapshot referenced. FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot tables. FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.

What is a SNAPSHOT LOG? - A snapshot log is a table in the master database that is associated with the master table. ORACLE uses a snapshot log to track the rows that have been updated in the master table. Snapshot logs are used in updating the snapshots based on the master table.

What is Distributed database? - A distributed database is a network of databases managed by multiple database servers that appears to a user as single logical database. The data of all databases in the distributed database can be simultaneously accessed and modified.

How can we reduce the network traffic? - Replication of data in distributed environment. - Using snapshots to replicate data. - Using remote procedure calls.

Differentiate simple and complex, snapshots? - A simple snapshot is based on a query thaat does not contains GROUP BY clauses, CONNECT BY clauses, JOINs, sub-query or snapshot of operations. - A complex snapshots contain at least any one of the above.

What are the Built-ins used for sending Parameters to forms? - You can pass parameter values to a form when an application executes the call_form, New_form, Open_form or Run_product.

Can you have more than one content canvas view attached with a window? - Yes. Each window you create must have at least one content canvas view assigned to it. You can also create a window that has manipulated content canvas view. At run time only one of the content canvas views assign to a window is displayed at a time.

Is the After report trigger fired if the report execution fails? - Yes.

Does a Before form trigger fire when the parameter form is suppressed? - Yes.

Is it possible to split the print reviewer into more than one region? - Yes

Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size? - Yes

For a field in a repeating frame, can the source come from the column which does not exist in the data group which forms the base for the frame? - Yes

Can a field be used in a report without it appearing in any data group? - Yes

The join defined by the default data link is an outer join yes or no? - Yes

Can a formula column referred to columns in higher group? - Yes

Can a formula column be obtained through a select statement? - Yes

Is it possible to insert comments into sql statements return in the data model editor? - Yes

Is it possible to disable the parameter from while running the report? - Yes

When a form is invoked with call_form, Does oracle forms issues a save point? - Yes

Can a property clause itself be based on a property clause? - Yes

If a parameter is used in a query without being previously defined, what diff. exist between report 2.0 and 2.5 when the query is applied? - While both reports 2.0 and 2.5 create the parameter, report 2.5 gives a message that a bind parameter has been created.

What are the SQL clauses supported in the link property sheet? - Where start with having.

What is trigger associated with the timer? - When-timer-expired.

What are the trigger associated with image items? - When-image-activated fires when the operators double clicks on an image itemwhen-image-pressed fires when an operator clicks or double clicks on an image item

What are the different windows events activated at runtimes? - When_window_activated
When_window_closed When_window_deactivated When_window_resized Within this triggers, you can examine the built in system variable system. event_window to determine the name of the window for which the trigger fired.

When do you use data parameter type? - When the value of a data parameter being passed to a called product is always the name of the record group defined in the current form. Data parameters are used to pass data to produts invoked with the run_product built-in subprogram.
What is difference between open_form and call_form? - when one form invokes another form by executing open_form the first form remains displayed, and operators can navigate between the forms as desired. when one form invokes another form by executing call_form, the called form is modal with respect to the calling form. That is, any windows that belong to the calling form are disabled, and operators cannot navigate to them until they first exit the called form.

What is new_form built-in? - When one form invokes another form by executing new_form oracle form exits the first form and releases its memory before loading the new form calling new form completely replace the first with the second. If there are changes pending in the first form, the operator will be prompted to save them before the new form is loaded.

What is the “LOV of Validation” Property of an item? - What is the use of it? - When LOV for Validation is set to True, Oracle Forms compares the current value of the text item to the values in the first column displayed in the LOV. Whenever the validation event occurs. If the value in the text item matches one of the values in the first column of the LOV, validation succeeds, the LOV is not displayed, and processing continues normally. If the value in the text item does not match one of the values in the first column of the LOV, Oracle Forms displays the LOV and uses the text item value as the search criteria to automatically reduce the list.

What is the diff. when Flex mode is mode on and when it is off? - When flex mode is on, reports automatically resizes the parent when the child is resized.

What is the diff. when confine mode is on and when it is off? - When confine mode is on, an object cannot be moved outside its parent in the layout.

What are visual attributes? - Visual attributes are the font, color, pattern proprieties that you set for form and menu objects that appear in your application interface.

Which of the two views should objects according to possession? - view by structure.

What are the two types of views available in the object navigator (specific to report 2.5)? - View by structure and view by type .

What are the vbx controls? - Vbx control provide a simple method of building and enhancing user interfaces. The controls can use to obtain user inputs and display program outputs.vbx control where originally develop as extensions for the ms visual basic environments and include such items as sliders, rides and knobs.

What is the use of transactional triggers? - Using transactional triggers we can control or modify the default functionality of the oracle forms.

How do you create a new session while open a new form? - Using open_form built-in setting the session option Ex. Open_form (’Stocks ‘,active,session). when invoke the mulitiple forms with open form and call_form in the same application, state whether the following are true/False
What are the ways to monitor the performance of the report? - Use reports profile executable statement. Use SQL trace facility.

If two groups are not linked in the data model editor, What is the hierarchy between them? - Two group that is above are the left most rank higher than the group that is to right or below it.

An open form can not be execute the call_form procedure if you chain of called forms has been initiated by another open form? - True

Explain about horizontal, Vertical tool bar canvas views? - Tool bar canvas views are used to create tool bars for individual windows. Horizontal tool bars are display at the top of a window, just under its menu bar. Vertical Tool bars are displayed along the left side of a window

What is the purpose of the product order option in the column property sheet? - To specify the order of individual group evaluation in a cross products.

What is the use of image_zoom built-in? - To manipulate images in image items.

How do you reference a parameter indirectly? - To indirectly reference a parameter use the NAME IN, COPY ‘built-ins to indirectly set and reference the parameters value’ Example name_in (’capital parameter my param’), Copy (’SURESH’,'Parameter my_param’)