18c Database : ASM DISK Groups Enhancements

In this post, we will see few important ASM Disk group Level Enhancements in 18c.

DISK_REPAIR_TIME : Increased from 3.5 hrs to 12 Hrs

When a disk is taken offline from a disk group , the diskgroup will not immediately dropped as it waits for 3.5 Hrs as DISK_REPAIR_TIME , but now that is changed to 12 Hrs. Until then Oracle ASM fast resync keeps track of pending changes to extents on an offline disk during an outage. The extents are resynced when the disk is brought back online.

FLEX Disk Groups : Convert a normal diskgroup to flex diskgroup without diskgroup mount restricted.

In 12cR2, Oracle introduced Flex Disk group to have more granularity at Database level usage of storage, by segregating the storage into file groups etc. The disk group can be converted from normal to flex diskgroup and then add a filegroups with for each diskgroup.  So to convert a normal diskgroup to a flex diskgroup the disk group must be in mount restricted mode.

In 18c, the mount restricted is not required for conversion you can convert the diskgroup from normal to flex diskgroup online.

Create a flex diskgroup
CREATE DISKGROUP flex_data FLEX REDUNDANCY DISK my_disk_discovery_path;
Diskgroup created.

Create a normal diskgroup
CREATE DISKGROUP normaltoflex NORMAL REDUNDANCY DISK '/devices/diskm*' ATTRIBUTE 'au_size'='4M', 'compatible.asm' = '18.0', 'compatible.rdbms' = '18.0','compatible.advm' = '18.0';
Diskgroup created.

Convert from Normal to Flex diskgroup
ALTER DISKGROUP normaltoflex CONVERT REDUNDANCY TO FLEX;

File Groups : Drop with cascade option

You can drop a file group including its associated files (drop including content) using the CASCADE keyword with the ALTER DISKGROUP ... DROP FILEGROUP SQL statement or the —r option with the ASMCMD rmfg command.

ALTER DISKGROUP DiskGroup_1 DROP FILEGROUP TEST CASCADE;

-Thanks

Suresh