Oracle DBA – A lifelong learning experience

Stopping diskmon on HP Itanium

Posted by John Hallas on January 26, 2009

A problem occurred on 2 node RAC cluster running on HP Itanium. The clusterware version was and we encountered a system crash with ORA-07445 errors

Exception [type: unknown signal, unknown code] [ADDR:0x0] [PC:0xC0000000004B1F50, __lwp_kill()+48] [exception issued by pid: 0, uid: 0]
Errors in file /app/oracle/diag/rdbms/database/SID/trace/SID_dskm_24740.trc (incident=128509):

We were asked if we had a diskmon process (init.cssd diskmon) running and we did have on production as well on the testing cluster (not intentionally and we still do not know how the process started). The ora_dskm process communicates with the diskmon process and this failure causes the instance to restart. DSKM (slave diskmon) is used as the conduit between RDBMS and ASM instances and the Master Diskmon daemon to communicate I/O Fencing information, I/O Resource Manager Plans, and Transaction Commit Cache information to SAGE storage.

I think SAGE storage refers to Exadata storage but I need to confirm this.

It transpires that there is an issue with a related component that is fixed in The fix has not been backported to

The diskmon process is not a required component of the clusterware when no exadata storage is there. It may be disabled in those cases. It is normally not running except on specific platform which are viewable in the
init.cssd script:
/* default for all platform is:
USING_DISKMON=’false’ # not using diskmon by default
/* but it is enabled for
case $PLATFORM in
USING_DISKMON=’true’ # using diskmon on this platform
HP-UX) MACH_HARDWARE=`/bin/uname -m`

USING_DISKMON=’true’ # using diskmon on this platform

Bug 7195402 show what need to be done to disable it,
work-around to disable the diskmon,
i.e. force USING_DISKMON in init.cssd to always be false so it never gets
started, i.e. edit the init.cssd,

1. go to the platform dependent section:

line 314: HP-UX) MACH_HARDWARE=`/bin/uname -m`

2. find the USING_DISKMON term

line 367
line 368 USING_DISKMON=’true’ # using diskmon on this platform
line 369

3. comment it to

368 #USING_DISKMON=’true’ # using diskmon on this platform

4. reboot the node

Our issue was then fixed. What is interesting is that we were brought down by a bug associated with Exadata and whilst Exadata uses HP hardware it is only available on OEL 5 not HPUX


2 Responses to “Stopping diskmon on HP Itanium”

  1. SAGE was the project name for Exadata: Storage Appliance for Grid Environments.

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