On the Fourth Day of 12.2, my DBA gave to me…

Automatic Storage Management New Features

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December 15, 2016

The following article will describe at a high-level the key ASM improvements in Oracle 12.2. Note, due to the number of changes and improvements in ACFS, we cover ACFS in a separate article.

Oracle ASM Flex Disk Groups and File Groups

In previous releases, disk group storage attributes were defined only at the disk group level, which was generally quite coarse from a storage management perspective. In 12.2, the concept of ASM flex disk group is introduced to enable users to manage storage at the database level, allowing greater granularity of control. Note, this capability is complimentary to the existing disk group manageability. Flex groups are built on the concept of File groups. File groups, are a group of files that share the same set of properties and characteristics and are used to describe database files. A significant benefit of file groups is the capability to have a different availability specification for each database; a key example is capability to create point-in-time database clones.

The following example illustrates how flex diskgroup is created.

SQL> create diskgroup vna_data flex redundancy disk ‘/dev/mapper/mpath*’

Or Convert existing standard diskgroup to flex diskgroup.

SQL> alter diskgroup vna_data convert redundancy to flex;

Each database that is built on ASM (that has compatible.asm and compatible.rdbms is set to 12.2.0.0) will consist of file group, which allows granular storage management capabilities, such as redundancy, rebalance power limits and priority, striping and quota groups; i.e., at the file group level. Since the redundancy is now at the file group level, and not at the disk group level, you can convert and change the redundancy of database from normal to high. Note, that you cannot currently change from external to high/normal.
Disk group can contain multiple file groups, each with its independent Flex redundancy. A file group can belong to only one disk group; however, a database can span multiple disk groups with multiple file groups in different disk groups.

ASM Support for Preferred Read on Extended Clusters

In previous releases the ASM_PREFERRED_READ_FAILURE_GROUPS defined read preference to a specific failure group in extended clusters.

In ASM 12.2, the preferred…

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