ORA-15041 - drop disks in ASM diskgroup

Test to drop disk in ASM Disk Group and found error: ORA-15041

SQL> alter diskgroup TEST_DG drop disks in failgroup EXACEL02 rebalance power 11 NOWAIT;

Diskgroup altered.

SQL> select * from gv$asm_operation;

INST_ID GROUP_NUMBER OPERA STAT POWER ACTUAL SOFAR EST_WORK EST_RATE EST_MINUTES ERROR_CODE
---------- ------------ ----- ---- ---------- ---------- ---------- ---------- ---------- ----------- ----------
1 4 REBAL ERRS 11 ORA-15041

SQL> select path, header_status, os_mb,free_mb, failgroup, mount_status from v$asm_disk where path like '%TEST_DG%' and failgroup='EXACEL02';

PATH HEADER_STATU OS_MB FREE_MB FAILGROUP MOUNT_S
---------------------------------------- ------------ ---------- ---------- ---------- -------
.
.
.
o/192.168.99.6/TEST_DG_FD_03_EXACEL02 FORMER 1024 0 EXACEL02 CLOSED
o/192.168.99.6/TEST_DG_FD_00_EXACEL02 MEMBER 1024 1012 EXACEL02 CACHED

MOUNT_STATUS should not be “CACHED” for DROPPED Disks.

ORA-15041: diskgroup space exhausted
Cause: The diskgroup ran out of space.
Action: Add more disks to the diskgroup, or delete some existing files.

Idea: Have to remove some files in this ASM disk group or add new disk to this ASM disk group, (Actually we can check "required_mirror_free_mb" in V$ASM_DISKGROUP before drop Disk). After we fixed it (this issue: I resized some database files):

SQL> select * from gv$asm_operation;

no rows selected

SQL> select path, header_status, os_mb,free_mb, failgroup, mount_status from v$asm_disk where path like '%TEST_DG%' and failgroup='EXACEL02';

PATH HEADER_STATU OS_MB FREE_MB FAILGROUP MOUNT_S
---------------------------------------- ------------ ---------- ---------- ---------- -------
.
.
.
o/192.168.99.6/TEST_DG_FD_03_EXACEL02 FORMER 1024 0 EXACEL02 CLOSED
o/192.168.99.6/TEST_DG_FD_15_EXACEL02 FORMER 1024 0 EXACEL02 CLOSED

Other Post: ORA-15041 - ASM Disk Group Unbalanced