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Error: Java.lang out of memory error: Perm gen space (Analyzing heap dump)

 
kona krishnakumar
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Hi All,

Recently in our new environment, we got out of memory and perm gen errors while doing deployment on weblogic server. I have taken heap dump using jmap command.

After that incresed the heap size from 1GB to 2GB and perm gen size from 512m to 640m. And then taken restart of weblogic instance and after that deployed application succesfully.

After analying the heap dump using IBM memory analyzer tool, foundt the following classloader errors in analyzer console.
=================================================================
20 instances of "weblogic.utils.classloaders.ChangeAwareClassLoader", loaded by "sun.misc.Launcher$AppClassLoader @ 0xc0000f40" occupy 2,42,85,568 (27.16%) bytes.

Biggest instances:

•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc14e0770 - 30,27,624 (3.39%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc149e270 - 21,77,352 (2.44%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc0dc9300 - 21,23,592 (2.38%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc4b299d8 - 21,19,592 (2.37%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc3d556c0 - 19,94,592 (2.23%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc3d51248 - 19,17,592 (2.14%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc1358b08 - 18,90,544 (2.11%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc3d51738 - 18,42,968 (2.06%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc1359358 - 18,30,656 (2.05%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc13662c8 - 18,24,680 (2.04%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc13f45b0 - 17,62,784 (1.97%) bytes.
•weblogic.utils.classloaders.ChangeAwareClassLoader @ 0xc4ed4ef8 - 17,07,752 (1.91%) bytes.

Keywords
sun.misc.Launcher$AppClassLoader @ 0xc0000f40
weblogic.utils.classloaders.ChangeAwareClassLoader
==============================================================

Did anyone faced this kind of issue in your environment and if possible kindly let me know how to prevent this kind of issues in future.

Thanks
Krishna
 
Abhinav Sonkar
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If the biggest instances as per the tool were ClassLoaders only then probably the configured PermGen space was too low. As a thumb rule, you can set PermGen space as 1/4th the Max JVM size.
 
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