Pmon Failed To Acquire Latch

"Pmon Failed To Acquire Latch" Messages in Alert Log -Database Hung [ID 468740.1]

Modified 15-SEP-2010     Type PROBLEM     Status MODERATED

Applies to: Oracle Server - Enterprise Edition - Version: 10.2.0.1 to 11.1.0.7 - Release: 10.2 to 11.1
Information in this document applies to any platform.
***Checked for relevance on 15-Sep-2010***

Symptoms

Database Instance hangs and connections to database using 'sqlplus' are also not possible.

Checking alert.log we see following messages

PMON failed to acquire latch, see PMON dump
Fri Oct 5 10:33:00 2007
PMON failed to acquire latch, see PMON dump
Fri Oct 5 10:34:05 2007
PMON failed to acquire latch, see PMON dump
Errors in file /dwrac/BDUMP/dwhp_pmon_1912834.trc:

This will also dump a systemstate dump and the location will be mentioned in alert.log

Also at OS level, we see that MMAN is consuming lot of CPU.






.

Cause

This issue was worked upon by development in

Bug 6488694 - DATABASE HUNG WITH PMON FAILED TO ACQUIRE LATCH MESSAGE
Bug 6488694 was closed as a duplicate of Bug 7039896.

Solution

Apply the patch for Bug 7039896.
Issue is fixed in:

• 11.2.0.1 (Base Release)
• 10.2.0.5 (Server Patch Set)
• 10.2.0.4.1 (Patch Set Update)

Workarounds that can be used:
Disable Automatic Shared Memory Management (ASMM) i.e Setting SGA_TARGET=0
or
Set the init.ora parameter _enable_shared_pool_durations=false