11g ASM New Features

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

■ ASM Fast Mirror Resync

A new SQL statement, ALTER DISKGROUP ... DISK ONLINE, can be executed
after a failed disk has been repaired. The command first brings the disk online for
writes so that no new writes are missed. Subsequently, it initiates a copy of all extents
marked 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 of
extents 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 compatibility
To enable some of the new ASM features, you can use two new disk group
compatibility attributes, compatible.rdbms and compatible.asm. These
attributes specify the minimum software version that is required to use disk
groups for the database and for ASM, respectively. This feature enables
heterogeneous environments with disk groups from both Oracle Database 10g and
Oracle Database 11g. By default, both attributes are set to 10.1. You must advance
these 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 and
restore operations in your ASM environment for faster recovery.

■ ASM fast rebalance

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

■ ASM Preferred Mirror Read

When ASM failure groups are defined, ASM can now read from the extent that is
closest to it, rather than always reading the primary copy. A new initialization
parameter, ASM_PREFERRED_READ_FAILURE_GROUPS, lets the ASM administrator
specify a list of failure group names that contain the preferred read disks for each node
in a cluster.

In an extended cluster configuration, reading from a local copy provides a great
performance 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 of
the nodes in the cluster are at different software versions. The various versions of the
software can still communicate with each other and provide a single system image.
The rolling upgrade capability will be available when upgrading from Oracle
Database 11g Release 1 (11.1).

This feature allows independent nodes of an ASM cluster to be migrated or patched
without affecting the availability of the database. Rolling upgrade provides higher
uptime 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 provides
near 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 up
to 64 MB.

■ Convert Single-Instance ASM to Clustered ASM

This feature provides support within Enterprise Manager to convert a non-clustered
ASM database to a clustered ASM database by implicitly configuring ASM on all
nodes. It also extends the single-instance to Oracle RAC conversion utility to support
standby databases.

Simplifying the conversion makes it easier for customers to migrate their databases
and 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 database
management and storage management responsibilities.
The SYSASM privilege allows an administrator to manage the disk groups that can be
shared by multiple databases. The SYSASM privilege provides a clear separation of
duties from the SYSDBA privilege.

For complete list of 11g ASM New Feature, You can refer the following

Note 551205.1 11g ASM New Features Technical White Paper
http://www.oracle.com/technology/pub/articles/oracle-database-11g-top-features/11g-asm.html