We have been dealing with a strange ASM  behavior over the past few months across all ASM instances in our multiple Oracle 11gR2 ( Cluster envs on HPUX 11.31 OS. Even a simple and typical ASM task like, adding new disk to ASM disk group, disk group mount/unmount and querying for CANDIDATE asm disks was taking min of 20 minutes, and sometimes infinity time. This behavior caused a lot of performance degradation across all database instance in the cluster, and most of the databases suffered with 'Disk file operations i/o' wait with other consequences.

I must say, Oracle support indeed made a few unsuccessful attempts by suggesting increasing the ASM instance SGA, enabling async i/o on OS, reducing the number of disks etc to address the issue. Finally, they have logged a BUG '18223021' for our issue and we are yet to receive the fix.

Below are a few consequences of this behavior we are confronting:

  • Oracle 10g database instances running on the node where a new ASM disk being added to the existing disk group had suffered with control file locking and database hung issues
  • We ensure the disk group to which a new disk is being added is not mounted on non relative ASM instances (in other nodes)
  • When adding disk takes infinite time on one of the ASM instances, the only way was to shutdown the instance with dismount the ASM disk group subsequently to speed-up and complete the procedure
  • Most databases are suffering with 'Disk File operations I/O'

If you have MOS access, you may refer the BUG for more details.

Stay tuned for the fix and solution...

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