Two APARs all WebSphere Application Server zOS 8002 customers should consider applying -

PM51889: DECREASE CLUSTER STARTUP TIME.

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* USERS AFFECTED:  All IBM WebSphere Application Server V8.0  users of Base and Network Deployment  editions.                              
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* PROBLEM DESCRIPTION: Excessive JIT compilation increases  the start time of servers and clusters             
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* RECOMMENDATION:                                            
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The Java JIT compiler provides a performance boost by compiling frequently used classes in such a way that future invocations of those classes perform better.  However, the initial compilation of these classes takes additional time. For classes that are used often throughout the life of the server, it is worth taking the initial time to compile them in order to obtain future performance benefits.During server startup, numerous classes are loaded that will rarely be invoked after startup is complete.  Compiling all of these classes is often unnecessary and can increase server start time.  The JIT compiler should be optimzied to avoid unnecessary compilations during server startup.
Problem conclusion
WebSphere Application Server was modified to inform the JIT compiler of the beginning and end of server  startup.  The JIT compiler can use this information to make better decisions about which classes to compile, thereby improving the start time of servers and clusters.

Fix on 8002: http://www.ibm.com/support/fixcentral/quickorder?product=ibm/WebSphere/WebSphere+Application+Server&fixids=8.0.0.2-WS-WAS-IFPM51889&source=myna&myns=swgws&mynp=OCSSEQTP&mync=E

The fix for this APAR is currently targeted for inclusion in fix pack 8.0.0.3.  Please refer to the Recommended Updates page for delivery information:
http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980

PM55170: CPU CONSTRAINED DMGR + NODE STARTUP 95% SLOWER

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* USERS AFFECTED:  All IBM WebSphere Application Server V8.0              
*                  users of Base and Network Deployment                                          
*                  editions.                                                                                          
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* PROBLEM DESCRIPTION: Excessive JIT compilation increases  
*                      the time to federate nodes.          
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* RECOMMENDATION:                                            
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The Java JIT compiler provides a performance boost by compiling frequently used classes in such a way that future invocations of those classes perform better.  However, the initial compilation of these classes takes additional time.For classes that are not used often throughout the life of the addNode command, it is not worth taking the initial time to compile them as the JVM shuts down after the command completes.  Compiling all of classes is unnecessary and can increase the time to federate a node.  The JIT compiler should be optimzied to avoid unnecessary compilations during node federation.
Problem conclusion
WebSphere Application Server was modified to inform the JIT compiler of the beginning of the addNode command.  The JIT compiler can use this information to make better decisions
about which classes to compile, thereby improve the federate a node.

The fix for this APAR is currently targeted for inclusion in fix pack 8.0.0.3.
Fix on 8002: http://www.ibm.com/support/fixcentral/quickorder?product=ibm/WebSphere/WebSphere+Application+Server&fixids=8.0.0.2-WS-WAS-IFPM55170&source=myna&myns=swgws&mynp=OCSSEQTP&mync=E