在客户的11.2.0.2环境中，删除第一个磁盘组碰到了错误。

对于RAC环境而言，第一个创建的磁盘组中包含OCR、VOT和ASM的启动参数文件SPFILE，因此先要删除第一个磁盘组，意味着需要迁移OCR、VOT和SPFILE文件。不过这里碰到的情况没有那么复杂，因为当前环境并非RAC，而是单机上启动的ASM实例。

当删除第一个磁盘组上所有的表空间后，尝试删除磁盘组报错：

[grid@dbserver1 ~]$ sqlplus / as sysasm

SQL*Plus: Release 11.2.0.2.0 Production on Tue Aug 16 10:16:23 2011

Copyright (c) 1982, 2010, Oracle. All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Automatic Storage Management option

SQL> set lines 120 pages 100
SQL> drop diskgroup DATA_AU1M;
drop diskgroup DATA_AU1M
*
ERROR at line 1:
ORA-15039: diskgroup not dropped
ORA-15053: diskgroup "DATA_AU1M" contains existing files

SQL> drop diskgroup DATA_AU4M;

Diskgroup dropped.

另一个磁盘组则在删掉所有的表空间后顺利删除。

检查发现ASM启动的SPFILE文件还保存在DATA_AU1M磁盘组中，如果强制删除，则会导致ASM实例无法启动。

SQL> show parameter spfile

NAME TYPE VALUE
-------------- --------- ------------------------------
spfile string +DATA_AU1M/asm/asmparameterfile/registry.253.758304963

利用CREATE PFILE FROM SPFILE创建一个文本的初始化参数：

SQL> create pfile from spfile;

File created.

SQL> host
[grid@dbserver1 ~]$ cd $ORACLE_HOME/dbs
[grid@dbserver1 dbs]$ ls
ab_+ASM.dat hc_+ASM.dat init+ASM.ora init.ora orapw+ASM
[grid@dbserver1 dbs]$ more init+ASM.ora
+ASM.__large_pool_size=25165824
+ASM.asm_diskgroups='DATA_AU2M','DATA','DATA_AU8M'#Manual Dismount
*.asm_diskstring='/dev/asm*'
*.asm_power_limit=1
*.diagnostic_dest='/u01/app/grid'
*.instance_type='asm'
*.large_pool_size=12M
*.local_listener='LISTENER_+ASM'
*.remote_login_passwordfile='EXCLUSIVE'

初始化参数中ASM_DISKGROUPS中并没有包含第一个磁盘组DATA_AU1M，而尝试利用这个PFILE启动也会发现，DATA_AU1M并没有加载：

[grid@dbserver1 dbs]$ exit
exit

SQL> shutdown immediate
ASM diskgroups dismounted
ASM instance shutdown
SQL> startup pfile=?/dbs/init+ASM.ora
ASM instance started

Total System Global Area 283930624 bytes
Fixed Size 2225792 bytes
Variable Size 256539008 bytes
ASM Cache 25165824 bytes
ASM diskgroups mounted
SQL> select group_number, name from v$asm_diskgroup;

GROUP_NUMBER NAME
------------ ------------------------------
1 DATA_AU2M
2 DATA_AU8M
3 DATA
0 DATA_AU1M

SQL> show parameter spfile

NAME TYPE VALUE
-------------- --------- ------------------------------
spfile string

下面编辑PFILE，添加DATA_AU1M磁盘组到初始化参数ASM_DISKGROUPS中，再次启动ASM实例：

SQL> shutdown immediate
ASM diskgroups dismounted
ASM instance shutdown
SQL> startup pfile=?/dbs/init+ASM.ora
ASM instance started

Total System Global Area 283930624 bytes
Fixed Size 2225792 bytes
Variable Size 256539008 bytes
ASM Cache 25165824 bytes
ASM diskgroups mounted
SQL> select group_number, name from v$asm_diskgroup;

GROUP_NUMBER NAME
------------ ------------------------------
1 DATA_AU1M
2 DATA_AU2M
3 DATA_AU8M
4 DATA

下面创建SPFILE，指定其他的磁盘组存放：

SQL> create spfile='+DATA' from pfile='/u01/app/grid/product/11.2.0/gridhome_1/dbs/init+ASM.ora';

File created.

SQL> shutdown immediate
ASM diskgroups dismounted
ASM instance shutdown
SQL> startup
ASM instance started

Total System Global Area 283930624 bytes
Fixed Size 2225792 bytes
Variable Size 256539008 bytes
ASM Cache 25165824 bytes
ASM diskgroups mounted
SQL> show parameter spfile

NAME TYPE VALUE
-------------- --------- ------------------------------
spfile string +DATA/asm/asmparameterfile/registry.253.759323107
SQL> select group_number, name from v$asm_diskgroup;

GROUP_NUMBER NAME
------------ ------------------------------
1 DATA_AU1M
2 DATA_AU2M
3 DATA_AU8M
4 DATA

对于ASM磁盘组而言，最后一个提供给它的SPFILE会自动作为ASM启动的SPFILE，不需要在文件系统中通过PFILE来指定，这是11.2中ASM自启动的机制。

下面可以强制删除磁盘组了，不过最好的办法是先删除问题，通过ASMCMD可以轻松的实现，而在ASM实例中也可以通过DROP FILE的方式实现：

SQL> drop diskgroup data_au1m;
drop diskgroup data_au1m
*
ERROR at line 1:
ORA-15039: diskgroup not dropped
ORA-15053: diskgroup "DATA_AU1M" contains existing files

SQL> select a.name, type
2 from v$asm_alias a, v$asm_file b
3 where a.group_number = 1
4 and b.group_number = 1
5 and a.file_number = b.file_number;

NAME TYPE
------------------------------ --------------------
REGISTRY.253.758304963 ASMPARAMETERFILE

SQL> alter diskgroup data_au1m drop file '+DATA_AU1M/asm/asmparameterfile/registry.253.758304963';

Diskgroup altered.

SQL> drop diskgroup data_au1m;

Diskgroup dropped.