ASM New Features in Oracle11g

The new features in Automatic Storage Management (ASM) extend the storagemanagement automation, improve scalability, and further simplify management forOracle Database files.

■ ASM Fast Mirror Resync A new SQL statement, ALTER DISKGROUP ... DISK ONLINE, can be executedafter a failed disk has been repaired. The command first brings the disk online forwrites so that no new writes are missed. Subsequently, it initiates a copy of all extentsmarked as stale on a disk from their redundant copies.This feature significantly reduces the time it takes to repair a failed diskgroup,potentially from hours to minutes. The repair time is proportional to the number ofextents that have been written to or modified since the failure.

■ ASM Manageability Enhancements The new storage administration features for ASM manageability include the following:

■ New attributes for disk group compatibilityTo enable some of the new ASM features, you can
use two new disk groupcompatibility attributes, compatible.rdbms and compatible.asm. Theseattributes specify the minimum software version that is required to use diskgroups for the database and for ASM, respectively. This feature enablesheterogeneous environments with disk groups from both Oracle Database 10g andOracle Database 11g. By default, both attributes are set to 10.1. You must advancethese attributes to take advantage of the new features.

■ New ASM command-line utility (ASMCMD) commands and options ASMCMD allows ASM disk identification, disk bad block repair, and backup andrestore operations in your ASM environment for faster recovery.

■ ASM fast rebalance Rebalance operations that occur while a disk group is in RESTRICTED modeeliminate the lock and unlock extent map messaging between ASM instances inOracle RAC environments, thus improving overall rebalance throughput.This collection of ASM management features simplifies and automates storagemanagement for Oracle databases.

■ ASM Preferred Mirror Read When ASM failure groups are defined, ASM can now read from the extent that isclosest to it, rather than always reading the primary copy. A new initializationparameter, ASM_PREFERRED_READ_FAILURE_GROUPS, lets the ASM administratorspecify a list of failure group names that contain the preferred read disks for each nodein a cluster. In an extended cluster configuration, reading from a local copy provides a greatperformance advantage. Every node can read from its local diskgroup (failure group),resulting in higher efficiency and performance and reduced network traffic.

■ ASM Rolling Upgrade Rolling upgrade is the ability of clustered software to function when one or more ofthe nodes in the cluster are at different software versions. The various versions of thesoftware can still communicate with each other and provide a single system image.The rolling upgrade capability will be available when upgrading from OracleDatabase 11g Release 1 (11.1). This feature allows independent nodes of an ASM cluster to be migrated or patchedwithout affecting the availability of the database. Rolling upgrade provides higheruptime and graceful migration to new releases.

■ ASM Scalability and Performance Enhancements This feature increases the maximum data file size that Oracle can support to 128 TB.ASM supports file sizes greater than 128 TB in any redundancy mode. This providesnear unlimited capacity for future growth. The ASM file size limits are:

■ External redundancy - 140 PB

■ Normal redundancy - 42 PB

■ High redundancy - 15 PB Customers can also increase the allocation unit size for a disk group in powers of 2 upto 64 MB.

■ Convert Single-Instance ASM to Clustered ASM This feature provides support within Enterprise Manager to convert a non-clusteredASM database to a clustered ASM database by implicitly configuring ASM on allnodes. It also extends the single-instance to Oracle RAC conversion utility to supportstandby databases. Simplifying the conversion makes it easier for customers to migrate their databasesand achieve the benefits of scalability and high availability provided by Oracle RAC.

■ New SYSASM Privilege for ASM Administration This feature introduces the new SYSASM privilege to allow for separation of databasemanagement and storage management responsibilities.The SYSASM privilege allows an administrator to manage the disk groups that can beshared by multiple databases. The SYSASM privilege provides a clear separation ofduties from the SYSDBA privilege. For complete list of 11g ASM New Feature, You can refer the following

Note: Metalink Id: 551205.1 11g ASM New Features Technical White

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