Reset ASM

Question

Hey folks
Is there a way to reset the ASM Instance. I mean, where does ASM stores the information e.g. the diskgroup name etc..? there is nowhere an controlfile or something similar.
the reason is: I can't drop my diskgroup because i can't mount them anymore. I think my fault was, that I include in asm_diskstring all four device files. I use an EVA.
SQL> alter system set asm_diskstring='/dev/rdsk/c*t*d*' scope=both;
System altered.
SQL> show parameter asm_diskstr
NAME                                 TYPE        VALUE
asm_diskstring                       string      /dev/rdsk/c*t*d*
SQL> select path from v$asm_disk;
PATH
/dev/rdsk/c8t0d6
/dev/rdsk/c2t0d6
/dev/rdsk/c4t0d6
/dev/rdsk/c6t0d6
...skip...
#this are the four device files
24 rows selected.
SQL> create diskgroup testing external redundancy disk '/dev/rdsk/c6t0d6';
create diskgroup testing external redundancy disk '/dev/rdsk/c6t0d6'
ERROR at line 1:
ORA-15018: diskgroup cannot be created
ORA-15030: diskgroup name "TESTING" is in use by another diskgroup
SQL> select name,state from v$asm_diskgroup;
NAME                           STATE
TESTING                        DISMOUNTED
SQL> alter diskgroup testing mount;
alter diskgroup testing mount
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15024: discovered duplicately numbered ASM disk 0
SQL> !oerr ORA 15024
15024, 00000, "discovered duplicately numbered ASM disk %s"
// *Cause:  The discovery encountered two disks claiming to have the same
//          ASM disk number.
// *Action: Check that the ASM_DISKSTRING parameter specifies only a
//          single path for each disk.
#change it to one path
SQL> alter system set asm_diskstring='/dev/rdsk/c6t0d6' scope=both;
System altered.
SQL> select name,state from v$asm_diskgroup;
NAME                           STATE
TESTING                        DISMOUNTED
SQL> alter diskgroup testing mount;
alter diskgroup testing mount
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15063: ASM discovered an insufficient number of disks for diskgroup
"TESTING"
SQL> drop diskgroup testing;
drop diskgroup testing
ERROR at line 1:
ORA-15039: diskgroup not dropped
ORA-15001: diskgroup "TESTING" does not exist or is not mountedwhere does ASM store the diskgroup name "testing"?
is there a way to reset the whole ASM configuration?
I have already deleted the device files and recreate them with insf -e.
OS: HPUX 11.23
ASM:10.2.0.3
Any ideas?
Regards Oviwan

Answer 1

Hi,
I got a pretty similar setup, and can immagine what you're going through :)
First of all, your main question: The DISKGROUP information is stored at the beginning of each raw disk. Hence if you've got 4 LUNs from the eva presented to your host and create a diskgroup from it, at the beginning of each disk, this information will be stored.
If you want to brute-force-remove the ASM diskgroup, you can use the friendly "dd"dd if=/dev/null of=/dev/rdsk/c8t0d6 bs=4096 count=1024As it's a multipathing device, you don't need to do it on every path of the LUN, just one of them.
Your first problem:ORA-15024: discovered duplicately numbered ASM disk 0is because you show asm multiple path to the same LUN. That's bad habbit!
Your second problem:ORA-15063: ASM discovered an insufficient number of disks for diskgroup
"TESTING"You're not showing enough LUNs.. You must have created the DG over 2 vDisks and ASM sees only one (ASM_DISKSTRING?)
I've got a habit of not using directly the /dev/rdsk directory with ASM.
What I do is:
mkdir /dev/asm
ln -s /dev/dsk/c0t0d0 /dev/asm/DGA1
ln -s /dev/dsk/c0t0d1 /dev/asm/DGA2
Then in the ASM spfile, I just set ASM_DISKSTRING=/dev/asm/*... so ASM sees only one path, all the path info is in a central place (/dev/asm) and only one link is made even if you've got 4 paths to the device.
About multipathing note that if you're using autopath, you see the 4 paths (not as with spmgr), and you just pick one randomly. Autopath does the failover and loadbalancing automatically.
Ask away if you need more info.
Yoann.