The Summarization and Pruning Agent runs
in a Java™ virtual machine (JVM),
which uses the JDBC (Java Database
Connectivity) interface to communicate with the warehouse database.
If the maximum Java heap size
of the JVM is set to a low value, performance can be degraded by frequent
garbage collections.
The maximum Java heap size
is controlled by the
-Xmx option. By default, this option is
not specified in the
Summarization and Pruning Agent configuration
file. If this option is not specified, the default value used by Java applies as follows:
- Half the available memory with a minimum of 16 MB and a maximum
of 512 MB.
- Half the available memory with a minimum of 16 MB and a maximum
of 512 MB.
- Half the real memory with a minimum of 16 MB and a maximum
of 2 GB.
Note: The above values are from the IBM® Developer Kit and Runtime Environment, Java Technology Edition, Version
6 Diagnostics Guide.
To set the size of maximum Java heap
size for the
Summarization and Pruning Agent,
edit the configuration file (
KSYENV on Windows,
sy.ini on UNIX or Linux)
and modify the KSZ_JAVA_ARGS variable as shown below:
KSZ_JAVA_ARGS=-Xmx512m
- A maximum Java heap size
of 512 megabytes (shown in the example above) is adequate for most
environments.
- In addition to the “mx” Java parameter,
you can also specify the -verbose:gc Java runtime parameter, which causes diagnostic
messages related to garbage collection to be written to the log. If
there are an excessive number of garbage collection entries consider
increasing the size of the Java heap.
- For more information about Java heap
tuning parameters, see the IBM Developer
Kit and Runtime Environment, Java Technology
Edition, Version 6 Diagnostics Guide, which is available from http://www.ibm.com/developerworks/java/jdk/diagnosis.