IBM WebSphere Application Server Performance Cookbook

J9 Health Center Enable at Startup of Limited Duration

The Health Center agent is shipped with IBM Java and IBM Semeru Runtimes on z/OS (though not z/Linux), but it is not currently shipped with IBM Semeru Runtimes on other platforms, though there are some unsupported workarounds. The Health Center agent neither ships with nor works with HotSpot JVMs.

  1. Stop the JVM
  2. Append the following JVM options and change the number of minutes after which Health Center will stop (two runs so multiply duration times 2 for total gathering time; see notes below for why 2 runs are suggested):
    • WebSphere Liberty jvm.options: 
      -Xhealthcenter:level=headless
-Dcom.ibm.java.diagnostics.healthcenter.headless.run.number.of.runs=2
-Dcom.ibm.java.diagnostics.healthcenter.headless.run.duration=15
    • WAS traditional generic JVM arguments: 
      -Xhealthcenter:level=headless -Dcom.ibm.java.diagnostics.healthcenter.headless.run.number.of.runs=2 -Dcom.ibm.java.diagnostics.healthcenter.headless.run.duration=15
  3. Start the JVM
  4. After the number of minutes specified, gather *.hcd files from the working directory of the process. By default:
    • WebSphere Liberty: $LIBERTY/usr/servers/$SERVER/
    • WAS traditional: $TWAS/profiles/$PROFILE/

Warnings and notes:

  1. Sometimes HCDs gathered during startup may fail performing method address to method name lookups due to JVMTI_ERROR_CLASS_NOT_PREPARED (22). All method name mappings are re-gathered at the start of each new HCD. For this reason, the above example uses two runs and then the second HCD may be appended in the client to evaluate all methods.
  2. If the JVM could not be stopped gracefully, gather the temporary files from a subdirectory of the output called tmp_${STARTDAY}${STARTMONTH}${STARTYEAR}_${STARTHOUR}${STARTMINUTES}${STARTSECONDS}_
  3. Use the additional JVM option -Dcom.ibm.java.diagnostics.healthcenter.headless.output.directory=$DIR to redirect Health Center files to a different directory instead of the working directory.
  4. If using Liberty and you specify -Xtrace:buffers={2m,dynamic} to minimize Health Center method metadata loss, since Liberty defaults to an unlimited maximum thread pool designed to maximize throughput, consider capping this with <executor maxThreads="N" /> based on available native memory to avoid native memory exhaustion, or use a smaller -Xtrace buffer size such as -Xtrace:buffers={128k,dynamic} (or lower).
  5. We have observed that some monitoring agents cause problems with Health Center. Consider removing other monitoring agents that use -agentpath while using HealthCenter, engage IBM and the agent company support teams to investigate, or use -Xbootclasspath/p to healthcenter.jar and -agentpath to libhealthcenter.so.

For details, see the Health Center chapter.