2.3.3.2 Shrink the Oracle ASM Disks in the Donor Disk Group

If there is no free space available on the cell disks, you can reduce the space used by one disk group to provide additional disk space for a different disk group.

This task is a continuation of an example where space in the RECOC1 disk group is being reallocated to the DATAC1 disk group.

Before resizing the disk group, make sure the disk group you are taking space from has sufficient free space.

1. Shrink the Oracle ASM disks for the RECO disk group down to the new desired size for all disks.

   Use the new size for the disks in the RECO disk group that was calculated in Step 5 of Determine the Amount of Available Space.

   SQL> ALTER DISKGROUP recoc1 RESIZE ALL SIZE 282672M REBALANCE POWER 64;

   Note:

   The ALTER DISKGROUP command may take several minutes to complete. The SQL prompt will not return until this operation has completed.

   If the specified disk group has quorum disks configured within the disk group, then the ALTER DISKGROUP ... RESIZE ALL command could fail with error ORA-15277. Quorum disks are configured if the requirements specified in Managing Quorum Disks for High Redundancy Disk Groups are met.

   As a workaround, for regular storage server failure groups (FAILGROUP_TYPE=REGULAR, not QUORUM), you can specify the failure group names explicitly in the SQL command, for example:

   SQL> ALTER DISKGROUP recoc1 RESIZE DISKS IN FAILGROUP exacell01 SIZE 282672M,
   exacell02 SIZE 282672M, exacell03 SIZE 282672M REBALANCE POWER 64;

   Wait for rebalance to finish by checking the view GV$ASM_OPERATION.

   SQL> set lines 250 pages 1000
   SQL> col error_code form a10
   SQL> SELECT dg.name, o.*
     2  FROM gv$asm_operation o, v$asm_diskgroup dg
     3  WHERE o.group_number = dg.group_number;

   Proceed to the next step ONLY when the query against GV$ASM_OPERATION shows no rows for the disk group being altered.

2. Verify the new size of the ASM disks using the following queries:

   SQL> SELECT name, total_mb, free_mb, total_mb - free_mb used_mb,
     2   ROUND(100*free_mb/total_mb,2) pct_free
     3  FROM v$asm_diskgroup
     4  ORDER BY 1;
   
   NAME                             TOTAL_MB    FREE_MB    USED_MB   PCT_FREE
   ------------------------------ ---------- ---------- ---------- ----------
   DATAC1                           68812800    9985076   58827724      14.51
   RECOC1                           47488896   35103336   12385560      73.92
   
   SQL> SELECT dg.name, d.total_mb, d.os_mb, COUNT(1) num_disks
     2  FROM v$asm_diskgroup dg, v$asm_disk d
     3  WHERE dg.group_number = d.group_number
     4  GROUP BY dg.name, d.total_mb, d.os_mb;
   
   NAME                             TOTAL_MB      OS_MB  NUM_DISKS
   ------------------------------ ---------- ---------- ----------
   DATAC1                             409600     409600        168
   RECOC1                             282672     565360        168

   The above query example shows that the disks in the RECOC1 disk group have been resized to a size of 282672 MG each, and the total disk group size is 47488896 MB.