PM12460; 7.0.0.9: High memory use when annotations are used with Array objects.

Download Description

PM12460 resolves the following problem:

ERROR DESCRIPTION:
Extra memory utilization will be seen when annotations are used in relation to an Array type. A static reference is created to a J2EE module, but this can lead to the associated memory being held on to for a longer duration than needed. In some circumstances, the amount of memory could be significant being withheld could be significant.

LOCAL FIX:
N/A

PROBLEM SUMMARY:

USERS AFFECTED:
All users of IBM WebSphere Application Server who use JavaEE5 enabled applications with annotations.

PROBLEM DESCRIPTION:
Extra memory utilization will be seen when annotations are used in relation to an Array type.

RECOMMENDATION:
None

Extra memory utilization may be seen when java class information is processed for annotation scanning steps, which are performed when loading application and module metadata for JavaEE5 enabled applications and application modules.

Extra allocations occur because of a static cache holding a reference to class information for java.lang.Object. The reference holds a secondary reference to an application module. That causes the first module that was processed for annotations to be held by reference and to prevent that first module from being reclaimed by java garbage collection, even after the application module goes out of use.

The effect is to hold the data for single application in memory. The actual impact depends on the size of the first module to be processed. For small modules, the impact is relatively small (up to several megabytes of unreclaimed allocations). For very typical application modules, the impact can be much larger. When this problem was detected, a memory allocation of slightly more than 60 megabytes was noted.

PROBLEM CONCLUSION:
A code update was made to remove the static reference to class information for java.lang.Object.

The fix for this APAR is currently targeted for inclusion in fix pack 7.0.0.13. Refer to the Recommended Updates page for delivery information:
http://www.ibm.com/support/docview.wss?uid=swg27004980