DB2 - Problem description
Problem IT20400 | Status: Closed |
SUBOPTIMAL PERFORMANCE MAY PERSIST ON AN STMM-TUNED SYSTEM DUE TO LARGE CONSUMER NOT GIVING UP MEMORY | |
product: | |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 | |
Problem description: | |
On an STMM-tuned system, when there is a very large memory consumer that suddenly becomes idle (in very little need of memory), and there is no need to reassign that memory to other consumers for a lengthy period (>= 2 hours), STMM may subsequently not give memory to other needy consumers (eg. when workload ramps up). This occurs because of conflicting heuristics in STMM's tuning model. A consumer for which historical statistics are "weak" will release memory in small amounts. But those calculated amounts may be cancelled out when a separate minimum decrease size threshold test is applied. This situation is rare as the stubborn consumer must be very large, the demands of the other consumers modest, and, as stated above, there must be a fairly specific and extreme pattern in memory demands among the STMM-tuned memory consumers. | |
Problem Summary: | |
**************************************************************** * USERS AFFECTED: * * ALL * **************************************************************** * PROBLEM DESCRIPTION: * * See Error Description * **************************************************************** * RECOMMENDATION: * * Upgrade to Db2 10.5 Fix Pack 9 or higher * **************************************************************** | |
Local Fix: | |
Dynamically decrease the configuration of the stubborn large consumer in 25% decrements, waiting for ~5 minutes between each step before determining if tuning has normalized. i.e. db2 connect to <database> db2 alter/update <STMM consumer>... AUTOMATIC | |
Solution | |
First fixed in Db2 10.5 Fix Pack 9 | |
Workaround | |
not known / see Local fix | |
Timestamps | |
Date - problem reported : Date - problem closed : Date - last modified : | 28.04.2017 29.09.2017 29.09.2017 |
Problem solved at the following versions (IBM BugInfos) | |
9.0. | |
Problem solved according to the fixlist(s) of the following version(s) |