On HP, Linux, and Solaris, DB2 private memory set allocations
cannot be reduced by other memory areas.
Freeing activity in the private memory set itself can reduce
memory usage, but nothing can be decommitted from outside
This means that the "cached" instance memory should really be 0
for private memory.
Since STMM tunes memory based on being able to force down the
private cached memory in order to support additional database
memory, STMM database memory targets can be too high, causing
tuning failures and possible performance issues from contention
at the Instance Memory level.
This problem only impacts environments with a fixed Instance
Memory limit on HP, Linux, and Solaris where private memory
usage is high relative to the overall instance memory usage.
Example db2diag.log entries:
2011-01-29-18.00.22.920729-360 I3501E963 LEVEL:
Warning
PID : 14476 TID : 47766453610816PROC :
db2sysc 0
INSTANCE: db2inst1 NODE : 000 DB : SAMPLE
APPHDL : 0-26 APPID: *LOCAL.DB2.110129031555
AUTHID : db2inst1
EDUID : 129 EDUNAME: db2stmm (SAMPLE) 0
FUNCTION: DB2 UDB, SQO Memory Management,
SqloMemController::requestMemory, probe:50
MESSAGE : ZRC=0x8B0F0000=-1961951232=SQLO_NOMEM "No Memory
Available"
DIA8300C A memory heap error has occurred.
DATA #1 : String, 28 bytes
Attempt to get memory failed
DATA #2 : unsigned integer, 8 bytes
1206583296
DATA #3 : unsigned integer, 8 bytes
10
< means STMM tried 10 times to steal cached memory >
...
FUNCTION: DB2 UDB, SQO Memory Management,
SqloMemController::getPartitionStats, probe:14
DATA #1 : <preformatted>
PRIVATE - Current size : 1522176 KB, HWM : 2930240 KB, Reserved
: 521600 KB
Private memory remains with a high cached value (the "Reserved"
lable is wrong, it should be "Cached", similar to db2pd
-dbptnmem output). |
****************************************************************
* USERS AFFECTED: *
* Systems on Solaris, Linux, HP with STMM tuning Database *
* Memory (SELF_TUNING_MEM = ON AND DATABASE_MEMORY = *
* AUTOMATIC) AND a fixed Instance Memory limit. *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to DB2 Version 9.5 Fix Pack 8 or higher. *
* Alternatively, use a fixed Database Memory setting to *
* control main DB2 memory usage as opposed to a fixed Instance *
* Memory setting *
**************************************************************** |
