PQ90664: THE MDB PROCESSING BEHAVIOR IS BEING CHANGED TO ENABLE THROTTLE AFTER (X+1) MESSAGES ARE RECEIVED WHERE MAXSESSIONS=X.

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APAR status
Closed as program error.

Error description
W502009 level of WebSphere for z/OS added code to honor a
throttle on the message listener port. The maxsessions setting
for the message listener port controls the number of messages
accepted before the code blocks. The blocking continues until
the messages received are processed by the servant.
.
In the specific case where there are more than one message
listener ports all set to maxsessions=1, the code blocks as soon
as 1 message is received. The code is being changed so that it
blocks after it exceeds the maxsessions limit. Currently it is
set to block as soon as the messages equal the maxsessions
value. The change will give a degree of parallelism in these
specific cases.
Local fix Problem summary
****************************************************************
* USERS AFFECTED: All users of WebSphere Application Server    *
*                 V5.0 for z/OS                                *
****************************************************************
* PROBLEM DESCRIPTION: Different behaviors are exposed for     *
*                      Scalable Messaging Support (Plan A) and *
*                      Generic Messaging Support (Plan B) when *
*                      multiple MDBs are listening to the same *
*                      queue by using independent listener     *
*                      ports with maxSession setting of 1 and  *
*                      each MDB has a message selector.        *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
When multiple MDBs are listening to the same queue by using
independent listener ports with maxSession setting of 1 and each
MDB has a message selector, messages from the queue are
delivered to the corresponding MDB. The throttle support blocks
message distribution when a messaging work request is enqueued
for every single message in the queue. This behavior differs
from the Generic Messaging (Plan B) where message distribution
is only blocked when a message is to be delivered to an MDB that
is already processing a message. For example, for a message
sequence of A,B,A,C messages would normally be delivered to
MDB_A and MDB_B before blocking. For Scalable Messaging, the
message is delivered to just MDB_A, the throttle waits for
message processing completion to continue delivery to MDB_B and
then MDB_C.
Problem conclusion
The MDB Throttle was modified to block only when the listener
port maxSession is exceeded. This allows messages to be
delivered to several MDBs in a semi-concurrent manner as the
Generic Messaging Support (Plan B).

APAR PQ90664 is associated with SERVICE LEVEL W502014 of
WebSphere Application Server V5.0 for z/OS.
Temporary fix Comments
APAR information
APAR number PQ90664
Reported component name WEBSPHERE FOR Z
Reported component ID 5655I3500
Reported release 500
Status CLOSED PER
PE NoPE
HIPER NoHIPER
Special Attention NoSpecatt
Submitted date 2004-06-25
Closed date 2004-08-05
Last modified date 2004-09-03

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:
PQ91092

Modules/Macros
BBOUBINF          

Publications Referenced

Fix information
Fixed component name WEBSPHERE FOR Z
Fixed component ID 5655I3500

Applicable component levels
R500 PSY UQ91441    UP04/08/23 P F408

  Fix is available
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Document Information


Current web document: swg1PQ90664.html
Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server for z/OS
Operating system(s):
Software version: 500
Software edition:
Reference #: PQ90664
IBM Group: Software Group
Modified date: Sep 3, 2004