Sometimes it can happen that the ASM contains empty System directories which cannot be removed. according to note 3751057.8 (alter diskgroup drop directory force removes system aliases) The system generated directories shoshould be removed automatically as soon as all it's files are removed. however this does not happen sometimes and a manual directory removal will fail:
SQL> set pages 2000
SQL> SELECT level, dir, sys, substr(lpad(' ',2*level,' ')||CONCAT('+'||gname,
SYS_CONNECT_BY_PATH(aname,'/')),1,60) full_path
FROM ( SELECT g.name gname, a.parent_index pindex, a.name aname,
a.reference_index rindex, a.ALIAS_DIRECTORY dir, a.SYSTEM_CREATED sys
FROM v$asm_alias a, v$asm_diskgroup g
WHERE a.group_number = g.group_number)
START WITH (MOD(pindex, POWER(2, 24))) = 0
CONNECT BY PRIOR rindex = pindex
ORDER BY rtrim(ltrim(full_path))desc, level asc;
3 N Y +DATA/UDWH/DATAFILE/ADASTRA.376.624105133
2 Y Y +DATA/UDWH/DATAFILE
3 N Y +DATA/UDWH/CONTROLFILE/Current.486.624103637
3 N Y +DATA/UDWH/CONTROLFILE/Current.479.624103637
3 N Y +DATA/UDWH/CONTROLFILE/Current.434.624103637
2 Y Y +DATA/UDWH/CONTROLFILE
1 Y Y +DATA/UDWH
1 Y Y +DATA/TDWH
2 N N +DATA/IDWH/spfileIDWH.ora
2 N N +DATA/IDWH/control03.ctl
2 N N +DATA/IDWH/control02.ctl
2 N N +DATA/IDWH/control01.ctl
The tdwh directory from the above list is empty but cannot be removed:
ASMCMD> cd tdwh
ASMCMD> ls
ASMCMD> cd ..
ASMCMD> rm -rf tdwh
ORA-15032: not all alterations performed
ORA-15177: cannot operate on system aliases (DBD ERROR: OCIStmtExecute)
alter diskgroup DATA drop directory '+DATA/TDWH' FORCE;
ORA-15032: not all alterations performed
ORA-15177: cannot operate on system aliases (DBD ERROR: OCIStmtExecute)
A solution to remove these directories is to recreate the ASM diskgroups but this is not something one wocould do very often especially when the ASM is used by production databases.
Solution
Either:
Create a new database with the dbca having the same name as the old directory and subsequently drop the database with the dbca.
Or:
Create a dummy tablespace having a datafile within the directory to be dropped, drop the tablespace and then remove the datafile using the asmcmd tool. The old directory will be removed automatically.
There is a scenario when there are left behind directories after the database is dropped using rman's command "drop database including backups [noprompt];". when one falls into this there is no way out but to recreate the diskgroups. this problem is being investigated in bug 6606689. to avoid this issue one shoshould run the following two commands instead of "drop database including backups ;":
RMAN> Delete backupset;
RMAN> drop database;
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