PK96849: STACK OVERFLOW IF THE C STACK IS LARGER THAN THAN THE JAVA STACK- UNEXPECTED EXCEPTION IN THE JAVA API FRAMEWORK WITH JAVA UDNS

APAR status

• Closed as program error.

Error description

• A Java User Defined Node (UDN) is called twice in a message flow
  with other nodes inbetween. When the flow enters the evaluate
  method of the second instance, the flow rolls back and does not
  show an exception.
  
        catch( MbException ex )
  
  was added to the code to capture the exception and the following
  is produced in the trace:
  
        <com.ibm.broker.plugin.MbBrokerException  source:BIPv610
        key:4374 message:[BIPv610:4374]BIP4374S: An unexpected
        exception has occurred in the Java API framework.
  
  The error is also dependant on the number of nodes (any type)
  between the two Java Nodes. The more nodes there are, the
  greater the likelihood of failure.
  
  The cause of the failure is a system stack overflow error.
  
  The problem appears to be that the default Java stack size is
  not big enough to accommodate the large number of nodes between
  the two instances of the Java user-defined node. Also, The posix
  standard does not include an API that allows you to determine it
  dynamically, thus preventing a dynamic change of the stack.
  

Local fix

• It is possible to add the following Java env. variable to the
  brokers ENVFILE to increase the Java Stack size:
  
  IBM_JAVA_OPTIONS=-Xmso<size>
  ie.,
  IBM_JAVA_OPTIONS=-Xmso1048576
    (which is 1 MB)
  
  The EG will need to be restarted to pick up the change.
  

Problem summary

• ****************************************************************
  * USERS AFFECTED: All users of WebSphere Message Broker on     *
  *                 Unix and z/OS using large C/Java stack       *
  *                 sizes.                                       *
  ****************************************************************
  * PROBLEM DESCRIPTION: A Java stackoverflow may occur if the   *
  *                      C stack is larger than the Java stack   *
  *                      size.                                   *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  The JVM only attempts to determine the Java stack size on the
  Windows operating system. For all other platforms, it assumes
  that the stack size will be the same as the value set with
  with the Java -Xmso option. If the C thread stack size grows
  beyond this value and the thread then calls into Java, the
  stackoverflow exception will occur.
  

Problem conclusion

• WebSphere Message Broker has been modified so that the size of
  the Java stack is set to the same size as the C stack before
  the C thread calls into Java.
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Modules/Macros

• BIP610DQ BIP610DR BIP610DS BIP610DT BIP610DU BIP610DV BIP610DW
  BIP610DX BIP610DY BIP610DZ BIP610E0 BIP610
  
  ***This field was truncated.  To obtain the full apar record, please contact your local support center.***
  

Fix information

• Fixed component name

  WMB Z/OS V6

• Fixed component ID

  5655M7400

Applicable component levels

• R100 PSY

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