IBM Support

The first server startup after installing a fix pack might be slower due to class cache rebuild

Troubleshooting


Problem

The install (or uninstall) process for a WebSphere Application Server fix pack clears the Java class cache as well as the OSGi cache. These data caches are rebuilt the first time a server or utility is started after the fix pack is installed (or uninstalled). This results in a one-time performance impact, causing server and utility start-up time to be slower.

Symptom

During the installation process for WebSphere Application Server fix packs, the Java class cache and the OSGi cache data is purged. This automatically occurs as part of the fix pack install process, and it ensures that old versions of cached classes are not loaded from the cache after the product is updated. This is also true for fix pack uninstalls.

The purged data is regenerated the first time it is needed. As a consequence, the first time an application server and applications are started after a fix pack is installed, the startup process might be slower. This same effect occurs for some WebSphere Application Server utilities. Much of this data is cached per-profile, so this increase in startup time would be seen once on each profile.

Subsequent server startups will take advantage of the regenerated cache data, and will not be as slow as the first startup.

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Document Information

Modified date:
03 March 2025

UID

swg21418620

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