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DB2 - Problembeschreibung

Problem IC99068 Status: Geschlossen

SORTS FROM SMALL INDEX BUILDS OVER-RESERVE SORT MEMORY, STMM MAY
UNNECESSARILY INCREASE SORT TUNING

Produkt:
DB2 FOR LUW / DB2FORLUW / A50 - DB2
Problembeschreibung:
Index builds, including during reorg, reserve the full sortheap 
from sort memory.  Most index builds are done in parallel with 6 
subagents, so most reserve 6 full sortheaps.  Much of this 
memory may never be allocated for smaller index builds.  Since 
STMM tuning is based on the sort reservation, STMM may react by 
increasing the sort configuration, which may cause a subsequent 
index build to reserve even more memory. 
 
Generally there is no adverse symptom from this other than an 
STMM-tuned configuration may seem to set SHEAPTHRES_SHR and 
SORTHEAP unnecessarily high.  In extreme cases other STMM 
consumers may be decreased, causing some performance 
degradation. 
 
One method of determining this issue exists is by examining a 
database snapshot.  The high water mark for reserved shared sort 
usage: 
Shared Sort heap high water mark           = 70129 ( 4K pages ) 
 
May be much higher than the actual shared sort pool usage : 
    Memory Pool Type                           = Shared Sort 
Heap 
       Current size (bytes)                    = 0 
       High water mark (bytes)                 = 20512768 
       Configured size (bytes)                 = 307200000 
 
In this case, the highest reserved sort memory was 280 Mb (70129 
4K pages), but the actual allocated memory only reached 20MB 
(20512768 bytes).
Problem-Zusammenfassung:
**************************************************************** 
* USERS AFFECTED:                                              * 
* All systems                                                  * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 Version 10.5 Fix Pack 4                       * 
****************************************************************
Local-Fix:
configure sortheap, sheapthres_shr to fixed values
verfügbare FixPacks:
DB2 Cancun Release 10.5.0.4 (also known as Fix Pack 4) for Linux, UNIX, and Windows
DB2 Version 10.5 Fix Pack 9 for Linux, UNIX, and Windows

Lösung
Problem first fixed in DB2 Version 10.5 Fix Pack 4
Workaround
see Local Fix
Weitere Daten
Datum - Problem gemeldet    :
Datum - Problem geschlossen :
Datum - der letzten Änderung:
29.01.2014
22.09.2014
10.06.2016
Problem behoben ab folgender Versionen (IBM BugInfos)
Problem behoben lt. FixList in der Version
10.5.0.4 FixList