1. ASM File Group Parity Protection New to ASM for Oracle Database 19c
Jim Williams
ASM Product Manager
January, 2019

2. Simple Idea to Address Storage Management Complexity
Provide an integrated cluster volume manager and file system
Stripe and mirror files across disks in ASM Disk Groups
Automatic rebalance after storage configuration changes
Build on the Oracle instance architecture
I/O operations DO NOT go through the ASM instance!
Manage storage as a global cluster of shared Disk Groups
ASM is an purpose-built host based volume management and file system that is integrated with the Oracle database. It is built on the tried and true premise of stripping and mirroring files across as many disks as possible and providing the ability of rebalancing the file layout, online whenever the physical storage configuration changes.
ASM is build on the Oracle instance architecture and provides global and shared access to a relatively small number of Disk Groups.

3. Diskgroup Oriented Storage Management before 12.2
Pre-12.2 Diskgroup Organization
Diskgroup
DB3 : File 1
DB2 : File 2
DB1 : File 3
DB3 : File 3
DB2 : File 1
DB1 : File 1
DB1 : File 2
DB2 : File 3
DB3 : File 2
DB2 : File 4
Disk Groups contain files striped across disks and optionally mirrored
No distinction between individual databases
Easy to manage, but made database oriented management impossible
With respect to storage management, ASM has until now been Diskgroup-centric. You create a Diskgroup and store all your database files there.
In Oracle 12.2 ASM introduces a new style of management called Database Oriented Storage Management. Database Oriented Storage Management is made available with a new type of Diskgroup called the Flex Diskgroup. As before, we have External, Normal, and High Redundancy Diskgroups, and now we have a new type of Diskgroup called the Flex Diskgroup.
Flex Diskgroups enable a new concept of a File Group which is a logical container of files in a Diskgroup that belong to an individual database or PDB. The File Group’s name is usually the database or PDB name.
File Groups allow operations to be targeted against all the files belonging to a database collectively.
File Groups do not change the way ASM stripes files across the ASM Disks as before. The provide new management efficiency and a set of new capabilities.

4. 12.2 Introduced Database Oriented Storage Management
12.2 Flex Diskgroup Organization
Flex Diskgroup
DB1
File 1
File 2
File 3
DB2
File 4
DB3
File Group
File Group
New Disk Group type: Flex Disk Groups
Flex Disk Groups provide File Groups
A File Group is the collection of files belonging to individual databases or PDBs
A File Group’s name defaults to the database or PDB name
A key feature Flex Diskgroups and File Groups is quota management. Quota management is provided with Quota Groups.
Quota Groups are a way of specifying the amount of storage that a databases in a File Group can consume. You can have one File Group in a Quota Group or some number of File Groups in a single Quota Group. No longer will you need to put databases in their own Diskgroup to constrain the amount of storage space they consume.
Flex Diskgroups changes the way redundancy is handled. Rather than have a Diskgroup-wide redundancy setting that is fixed when the Diskgroup is created, redundancy for Flex Diskgroups is specified at the File Group level and is modifiable. Furthermore, for write once files such as archive logs and backups, parity protection similar to RAID 5 and 6 is available.
And lastly, with Flex Diskgroups, the redundancy of a File Group can be used to split off a copy of the File Group as a Shadow Copy of the File Group. When the Shadow Copy is split off, a new full instantiated File Group representing a copy of the database or PDB is created. This is perhaps one of the most requested capabilities for ASM and is available in Oracle 12c Release 2.

5. ASM File Group Flexibility and Availability
Flex Disk Groups enable
Quota Management - limit the space databases can allocate in a Disk Group and thereby improve the customers’ ability to consolidate databases into fewer Disk Groups
Redundancy Change – utilize lower redundancy for less critical databases
ASM Database Clones to easily and dynamically create database clones for test and development, or production databases
File groups allow administrators to have finer grained control over the files in the diskgroup.
They can specify and change the redundancy for files within a file group.
They can create a quota group to limit the space databases in one or more file groups can consume.
They can also create database clones, which are copies of the data (mirrors) that can be split off to form a new file group.
Thus, they can create a shadow copy, and then split that copy off to create a cloned database for test/dev or other uses.

6. Steps to Changing File Group Redundancy
Set compatibility to 18 (ASM instance)
alter diskgroup data set attribute 'compatible.asm' = ‘19.0';
alter diskgroup data set attribute 'compatible.rdbms' = ‘19.0';
Show new File Groups (ASM instance)
asmcmd lsfg -G DATA --filegroup FG1
Change File Group Protection
ALTER DISKGROUP ARC MODIFY FILEGROUP FileGroup_PDB1
SET 'archivelog.redundancy' = 'PARITY’;
Can be issued from database (sysdba) or ASM instance
Only new file creations will use parity. Existing files remain unchanged.
Confidential – Oracle Internal/Restricted/Highly Restricted

7. ASM Administration Guide