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Unexpected GC Spikes even though there is a free heap available.


Article ID: 8439


Updated On:


CA Application Performance Management Agent (APM / Wily / Introscope) INTROSCOPE


  EM/Workstation/Investigator are slow in logging and in general performance.


Unexplained GC spikes when there are plenty of free memory in heap could be caused by a known issue of LDAP login triggering explicit GC, This is because APM calls System.gc() in the code. This can be confirmed if there is also User login related message in the log corresponding to the GC spiking time.


This has occurred with APM 10.5.1 (HF 32 & HF 39) and 10.5.2 with various operating systems .


    The workaround is to disable explicit GC:

- Add Java option "XX:+DisableExplicitGC" for Oracle JVM

- "-Xdisableexplicitgc" for IBM JVM

More details on this Java option is covered in 


Additional Information