|
Problem IC74138
|
Status: Closed |
STMM FAILS TO USE EXCESS MEMORY IN USE BY FILE CACHE ON AIX WITH SMALL PAGING SPACE |
| product: |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 |
| Problem description: |
On AIX, STMM may fail to take away excess system memory from
file cache, and additionally may tune DB2 down at points when
most of the system memory is taken up by file cache.
This occurs only on systems with small paging space
configurations.
It will not impact environments using a fixed INSTANCE_MEMORY
value (STMM does not monitor system memory in this
configuration).
Various symptoms may be observed, including erratic STMM tuning,
performance degradation, and SQL1218 errors (no pages available
in bufferpool).
The problem is caused by DB2 capping the file cache it sees as
available by the amount of available paging space.
DB2 will deduct from this "capped available file cache" amount
allowances for uncommited DB2 memory, such as unused Utility
Heap. The result may be that DB2 / STMM sees the system as
memory constrained when it is not.
It is recognized that modern well-tuned AIX systems (AIX 5.3 and
higher) where memory requirements do not exceed capacity do not
require large paging space configurations, and therefore, under
normal operating conditions, available paging space should not
be a limiting factor in the "available file cache" calculation.
The workaround is to increase paging space to at least 50% of
RAM. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* DB2 servers on AIX with self-tuning of database memory *
* enabled and no Instance Memory limit (SELF_TUNING_MEM=ON, *
* DATABASE_MEMORY=AUTOMATIC, INSTANCE_MEMORY=AUTOMATIC) *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Avoid problem by following documented minimum paging space *
* recommendations. *
**************************************************************** |
| Local Fix: |
Increase paging space to at least 50% of RAM |
| available fix packs: |
DB2 Version 9.7 Fix Pack 5 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
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
|
| Solution |
Problem first fixed in DB2 Version 9.7 Fix Pack 5 |
| Workaround |
n/a |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 26.01.2011
27.02.2012
27.02.2012 |
| Problem solved at the following versions (IBM BugInfos) |
9.7.FP5
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.7.0.5
|
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