11gr2 mysteriously changing asm_diskgroup parameter.

A few days ago , I was checking a 11gr2 (11.2.0.1) Rac database , residing on AIX 6.1.

2 disk groups named DATA and FRA were created, and all files were on DATA.

I realized that FRA was never mounted by grid processes after a reboot or crs stop/start.

Here is the ways I tried , and costed me a couple of hours to understand what was happening.

1-ASM_DISKGROUPS parameter changed. RESULT: FAIL

2-creating a pfile , to check if settings are correct.

3-realizing instance scope settings.

4-change instance scope variables. but no help . RESULT: FAIL

5-understanding what was exactly happening, why the "ASM_DISKGROUPS " parameter changed.

6-setting dependency , solving problem.

1-

I just thougt that it was because of asm_diskgroups parameter. And just changed it.

ALTER SYSTEM SET ASM_DISKGROUPS='DATA','FRA' scope=both;

After changing that , I was expecting everything would became normal. But not.

I created a pfile from spfile to double check .

2-

create pfile='/tmp/hede8' from spfile='+DATA/personel/asmparameterfile/registry.253.733514437';

cat /tmp/hede8

+ASM1.asm_diskgroups='FRA'#Manual Mount

*.asm_diskgroups='DATA','FRA'

+ASM1.asm_diskgroups='FRA'#Manual Mount

*.asm_power_limit=1

*.diagnostic_dest='/oracle/app/oracle'

*.instance_type='asm'

*.large_pool_size=12M

*.remote_login_passwordfile='EXCLUSIVE'

3-

and saw the fallowing lines. Then there was a precedence.

+ASM1.asm_diskgroups='FRA'#Manual Mount

4-

again changed paramters as fallows

ALTER SYSTEM SET ASM_DISKGROUPS='DATA','FRA' scope=both sid='+ASM1';

After instance scope variables I was again expecting a good result. But what is that again. The parameter has seen changed again. I created pfile once more and yes the paramters which ı had changed in step 3 were gone .There must be something buggy if there is is not a ghost dba doing nasty things :) In one of the reference notes ; it is said to be resolved 11.2.0.2 Not tested yet.

5-What happens then ?

Some metalink search guided the solution as usual.

11gr2 asm was updating the asm_diskgroup parameter as diskgroups mounted,dismounted.

While stopping adn starting Grid you will see in asm alert.logfile:

Fri Jan 07 09:47:36 2011

SQL> ALTER DISKGROUP DATA DISMOUNT /* asm agent */

Fri Jan 07 09:47:37 2011

SQL> ALTER DISKGROUP FRA DISMOUNT /* asm agent */

Fri Jan 07 09:47:47 2011

Then ofcourse parameter will change.And because of none of the files reside in FRA ; only DATA is mounted while starting rdbms instance, so there is no dependency in rdbms and FRA asm diskgroup.

If I add a dependency then everthing will be as expected.

To add a depedency :

srvctl modify database -d trt4 -a 'DATA,FRA'

To see details :

srvctl config database -d trt4

Here are some reference notes:

1. 1059856.1 ASM Diskgroups are not mounted with spfile on ASM on next startup with crsctl command in 11gR2. [ID 1059856.1]
2. 987904.1 Additional Diskgroups Does Not Get Mounted When SRVCTL Is Used To Start And Shutdown ASM Instance [ID 987904.1]
3. http://download.oracle.com/docs/cd/E11882_01/server.112/e17110/initparams010.htm#I1010247