|
Problem IC77427
|
Status: Closed |
BUFFER POOL DECREASE / STMM HANG WAITING ON SPECIAL TEMP BUFFER POOL PAGE |
| product: |
DB2 FOR LUW / DB2FORLUW / 950 - DB2 |
| Problem description: |
Buffer pool decreases, often initiated by STMM, may hang for
long periods due to special system temporary pages that are
being held in the buffer pool. If STMM initiated the buffer
pool decrease, it will be hung and unable to respond to changes
in workload or memory availability.
The "special temp pages" in question are for internal system
temporary objects that are cached for reuse until application
termination. A common triggering scenario is performing
special operations such as create index or runstats on user
temporary tables (declared or created global temporary tables).
The workaround is to avoid decreasing or fix the sizes of
buffer pools associated with system temporary tablespaces. Note
that although the triggering activity may be associated with
user temporary tables in "user" temporary tablespaces, the
internal objects are created in the "system" temporary
tablespaces.
If STMM is inoperative for long periods of time, and user
temporary tables are commonly created on the system, this is the
likely source of the problem.
One way of determining that STMM is hung is that regular
configuration updates cease. A second is that the STMM logs
stop being updated. The STMM thread, db2stmm, regularly writes
messages to the STMM logs (in DIAGPATH/stmmlog). Note db2agent
threads may still write messages to the STMM logs.
A call stack of the db2stmm thread will show that it is in the
midst of a buffer pool decrease :
thread_wait
getConflictComplex
getConflict
getConflict
sqlbSecurePageProtection
sqlbRemInvalidPagesFromBufferPool
sqlbDecreaseBufferpoolSize
sqlbResizeBufferPool
sqlbAlterAutomaticBufferPool |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* All systems *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 9.5 Fix Pack 9 *
**************************************************************** |
| Local Fix: |
Fix the sizes of buffer pools associated with system temporary
table spaces. |
| available fix packs: |
DB2 Version 9.5 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.5 Fix Pack 10 for Linux, UNIX, and Windows
|
| Solution |
Problem first fixed in DB2 Version 9.5 Fix Pack 9 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 08.07.2011
12.06.2012
12.06.2012 |
| Problem solved at the following versions (IBM BugInfos) |
9.5.FP9
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.5.0.9
|
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