Oracle Automatic Storage Management 18c New Features

 

Converting Normal or High Redundancy Disk Groups to Flex Disk Groups without Restricted Mount

You can convert a conventional disk group (disk group created before Oracle ASM18c) to an Oracle ASM flex disk group without using the restrictive mount (MOUNTED
RESTRICTED) option

I have a NORMAL REDUNDANCY disk group named DG_FLEX. I will convert this DG to FLEX redundancy to demonstrate this new feature

Note: To Convert the diskgroup to FLEX redundancy without mounting it in restricted mode
Following is required

1> ASM Version 18c
2> 'compatible.asm' = '18.0.0.0.0';
3> 'compatible.advm'='18.0.0.0.0';
4> 'compatible.rdbms'='12.2.0.0.0' or higher;
5> 'VAM_MIGRATION_DONE'='true'

Virtual Allocation Metadata (VAM) migration must be enabled and completed
before converting without the use of a restrictive mount.

You can set the DG attributes of a disk group as shown below

SQL> ALTER DISKGROUP DG_FLEX SET ATTRIBUTE 'compatible.asm' = '18.0.0.0.0';

Diskgroup altered.

SQL> ALTER DISKGROUP DG_FLEX SET ATTRIBUTE 'compatible.advm'='18.0.0.0.0';

Diskgroup altered.

SQL> ALTER DISKGROUP DG_FLEX SET ATTRIBUTE 'compatible.rdbms'='18.0.0.0.0';

Diskgroup altered.

SQL> ALTER DISKGROUP DG_FLEX SET ATTRIBUTE  'VAM_MIGRATION_DONE'='true';

Diskgroup altered.

SQL> select DG.NAME,DG.STATE,DG.TYPE as REDUNDANCY,DS.STATE,DS.MODE_STATUS,DS.HEADER_STATUS,DS.MOUNT_STATUS,DS.NAME from v$asm_diskgroup dg,v$asm_disk ds where dg.GROUP_NUMBER=ds.GROUP_NUMBER and DG.NAME='DG_FLEX';

NAME                           STATE       REDUNDANCY STATE    MODE_ST HEADER_STATU MOUNT_S NAME
------------------------------ ----------- ---------- -------- ------- ------------ ------- -------------------
DG_FLEX                        MOUNTED     NORMAL     NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA02
DG_FLEX                        MOUNTED     NORMAL     NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA03

DG_FLEX                        MOUNTED     NORMAL     NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA01

SQL>  ALTER DISKGROUP DG_FLEX CONVERT REDUNDANCY TO FLEX;
Diskgroup altered.

SQL> select DG.NAME,DG.STATE,DG.TYPE as REDUNDANCY,DS.STATE,DS.MODE_STATUS,DS.HEADER_STATUS,DS.MOUNT_STATUS,DS.NAME from v$asm_diskgroup dg,v$asm_disk ds where dg.GROUP_NUMBER=ds.GROUP_NUMBER and DG.NAME='DG_FLEX';

NAME                           STATE       REDUNDANCY STATE    MODE_ST HEADER_STATU MOUNT_S NAME
------------------------------ ----------- ---------- -------- ------- ------------ ------- -------------------
DG_FLEX                        MOUNTED     FLEX       NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA02
DG_FLEX                        MOUNTED     FLEX       NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA03
DG_FLEX                        MOUNTED     FLEX       NORMAL   ONLINE  MEMBER       CACHED  FLEX_DATA01

Dropping Oracle ASM File Groups With a Cascade Option

starting with 18c you can drop a file group with Cascade option. This will drop all the associated files including content with this file group and you no longer need to manually cleanup them up.

SQL> ALTER DISKGROUP DG_FLEX DROP FILEGROUP FG_PDB1 CASCADE;
Diskgroup altered.

Point-In-Time Database Cloning With Oracle ASM Flex Disk Groups

Oracle ASM provides support for creating a point-in-time database clone which is a
mirror copy of a pluggable database. All the data files of the database being cloned
should be present in a single disk group. The cloning operation can be used for rapid
provisioning of identical copies. You can specify the redundancy setting of the
database data files in the database clone, or the setting can default to the redundancy
of the data files in the source database that is being the cloned. The Point in time cloning is done using following steps.

Step1> Preparing the Mirrored Copy
Step2> Splitting the Mirrored Copy and Creating the Database Clone
Step3> Dropping the Prepared Mirror Copy