DB2 FOR LUW / DB2FORLUW / 970 - DB2

Under out of memory or low memory conditions, a snapshot 
operation may lead to a 'dead latch', causing a hang in DB2. The 
'dead latch' is triggered by some 'Memory Allocation Error' in 
sqm_get_next_dbcb(), which is recorded in db2diag.log as 
follows: 
=========================================== 
2013-01-01-01.01.01.123456+789 I12345678901234    LEVEL: Error 
PID     : 12345678             TID  : 12345       PROC : db2sysc 
3 
INSTANCE: rdminst              NODE : 003 
APPHDL  : 0-1234 
EDUID   : 12345                EDUNAME: db2agent (idle) 3 
FUNCTION: DB2 UDB, database monitor, sqm___sqm_get_next_dbcb, 
probe:60 
MESSAGE : Memory Allocation Error 
=========================================== 
 
The problem is caused by EDUs waiting on latch 
SQLO_LT_sqeDBMgr__dbMgrLatch. 
 
For latch waiters, following stack traces will be seen in stack 
files: 
=========================================== 
sqloXlatchConflict 
sqloXlatchConflict 
sqm_get_next_dbcb 
sqlmonssagnt 
sqlmPdbRequestRouter 
 
Or 
 
sqloXlatchConflict 
sqloXlatchConflict 
StartUsingLocalDatabase 
AppStartUsing 
=========================================== 
 
For latch holder, it is stuck in following stack trace: 
=========================================== 
sqloXlatchConflict 
sqloXlatchConflict 
sqm_get_next_dbcb 
turn_off_switches 
update_switches 
=========================================== 
And in the "LatchInformation" section of the stack file, the 
holder is holding the SQLO_LT_sqeDBMgr__dbMgrLatch whilst 
waiting on the same latch too, which is a 'dead latch' situation 
that can only be resolved by killing the DB2 instance. Here is 
an example: 
=========================================== 
<LatchInformation> 
 
Waiting on latch type: (SQLO_LT_sqeDBMgr__dbMgrLatch) - Address: 
(780000000212121), Line: 278, File: sqlmutil.C 
 
Holding Latch type: (SQLO_LT_sqeDBMgr__dbMgrLatch) - Address: 
(780000000212121), Line: 278, File: sqlmutil.C HoldCount: 1 
</LatchInformation> 
===========================================

**************************************************************** 
* USERS AFFECTED:                                              * 
* All users of version 9.7 on Linux, Unix and Windows          * 
* platforms.                                                   * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Update to DB2 LUW Version 9.7 Fix Pack 9 or higher levels.   * 
****************************************************************

1. Find out the reason of the 'Memory Allocation Error', fix the 
issue to avoid the error. 
2. Avoid using snapshots under out of memory conditions.

DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
 DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows
 

First fixed in DB2 LUW Version 9.7 Fix Pack 9.

Find out the reason of the 'Memory Allocation Error', fix the 
issue to avoid the error.

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

06.03.2013
09.05.2014
09.05.2014

9.7.FP9