ASM (Automatic Storage Management) instances for the storage of database files have become a very popular option in the database world since the release of ORACLE 10g. However, there exist several administration concerns over ASM, which the DBA must take into consideration. This article covers the problem of ASM instance not starting after a reboot of a Linux server and applies to most Unix systems while using RAW Disks.

Error: ORA-15042: ASM disk is missing.

Reason: This error is caused by the RAW device being removed from the OS, corrupted, or/and most likely, not owned by the ORACLE user.

1. Verify that the ASM disk exists.

[root@mylinux1 /]# cd /dev/raw
[root@mylinux1 /dev/raw]# ls
/dev/raw/raw1
/dev/raw/raw2
/dev/raw/raw3
[root@mylinux1 u06]#

2. Check the ownership of the disks.

[root@mylinux1 /]# cd /dev/raw
[root@mylinux1 /dev/raw]# ls –la
-rw-r–r– 1 root root 2 Sep 2 08:33 raw1
-rw-r–r– 1 root root 2 Sep 2 08:33 raw2
-rw-r–r– 1 root root 2 Sep 2 08:34 raw3
[root@mylinux1 /dev/raw]#

NOTE: These raw devices are now owned by ROOT after the reboot, thus ORACLE does not have access.

3. On most UNIX systems you will see that the ownership of RAW devices is reset to ROOT after reboot. To correct this behavior, enter the following code into your init process before the Oracle database startup scripts are executed.

chown oracle:dba /dev/raw/raw1
chown oracle:dba /dev/raw/raw2
chown oracle:dba /dev/raw/raw3
Larry J Catt, OCP
oracle@allcompute.com
www.allcompute.com