PI80377: NEW ACTIVIATION SPEC PROPERTIES - CONTROL BUILD UP/FLOW OF MDB REQUESTS

Fixes are available

APAR status

Closed as program error.

Error description

Customer requested a finer grain approach for controlling the
build up of requests in relation to available server sessions
and memory requirements regarding MDB processing when using a
WebSphere MQ Activation Specification on z/OS.

WMQ Activation Specification driven MDBs on z/OS listen in the
Control Region Adjunct (CRA) which provides a throttle to
limit how many messages are concurrently processed by the
listener.

The size of the throttle is calculated as follows:

If the number of active servant regions is 0 then the throttle
limit is 0.

If the number of active servant regions is greater than 0 then
the throttle limit is number of active servants * maxPoolDepth
of Activation Spec * MaxInFlightMessagesScaleFactor +
MaxInFlightMessagesConstant.

By default the MaxInFlightMessagesScaleFactor is 1.0 and the
MaxInFlightMessagesConstant is 0.  The defaults can be
overriden by JVM system properties, but only on a JVM wide
basis, not per activation specification. There is no way to
configure an individual MDB listener's throttle to scale
with active servant regions in a manner that is independent of
the maxPoolDepth property.

In certain use cases it is desirable that:

- the servant regions are configured with a value of
maxPoolDepth that is high enough to prevent the Message Driven
Bean running in the servant region from blocking as it waits
for a free server session (while also consuming system
resources such as WLM enclaves)
- while at the same time being able to constrain the total
concurrent processing of messages for a specific listener via
the throttle in the control region adjunct in a manner
that scales with the number of available servant regions

This throttle behaviour is not possible with the configuration
options currently available.  Further configuration options
should be provided.

Local fix

Problem summary

****************************************************************
* USERS AFFECTED:  WebSphere Application Server users of       *
*                  WebSphere MQ Activation Specifications on   *
*                  z/OS.                                       *
****************************************************************
* PROBLEM DESCRIPTION: The configuration options of the        *
*                      throttle for MDBs listening in the      *
*                      Control Region Adjunct are too          *
*                      limited.                                *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
Message Driven Beans driven by WebSphere MQ Activation
Specifications listen in the control region adjunct which
provides a throttle to limit the number of messages that may
be processed concurrently.  One factor in calculating the
throttle size is the maxPoolDepth property of the related WMQ
Activation Specification, however this property also defines
the maximum number of Server Sessions available for the MDB in
the servant region.  It may be desirable that the throttle
size is configured independently of this value, in a manner
that scales with the number of active servant regions, and in
a manner that is unique to each activation specification.
This is not possible with the current set of options available
for configuring the throttle.

Problem conclusion

Message Driven Beans driven by WMQ Activation Specifications
on z/OS listen in the Control Region Adjunct (CRA) which
provides a throttle to limit how many messages are
concurrently processed by the listener.

The size of the throttle is calculated as follows:

If the number of active servant regions is 0 then the throttle
limit is 0.

If the number of active servant regions is greater than 0 then
the throttle limit is number of active servants * maxPoolDepth
of Activation Spec * MaxInFlightMessagesScaleFactor +
MaxInFlightMessagesConstant.

By default the MaxInFlightMessagesScaleFactor is 1.0 and the
MaxInFlightMessagesConstant is 0.

Throttle limits less than 0 are treated as 0.

The MaxInFlightMessagesConstant and
MaxInFlightMessagesScaleFactor used in this calulcation can be
modified using the following JVM system properties:
com.ibm.ws.wmqra.zdispatcher.MaxInFlightMessagesConstant
com.ibm.ws.wmqra.zdispatcher.MaxInFlightMessagesScaleFactor.
This effects the throttles for all MDBs listening in the CRA.

The default value of MaxInFlightMessagesConstant is 0.
The default value of MaxInFlightMessagesScaleFactor is 1.0F.

This APAR introduces three new properties that may be used to
control the throttle for each WMQ Activation Specification in
a manner that is both specific to each activation spec and
indpenent of the maxPoolDepth value.

The properties are configurable as new properties in the comma
separated string value of the "arbitrary properties" advanced
property of the WMQ Activation Specification for which the
properties are to apply.

The new properties are as follows:

was390_throttle_perSR:
If specified, this value overrides the use of the maxPoolDepth
when calculating the throttle size. This number may be 0 so
that the throttle is always a constant value, but may not be
negative.

was390_throttle_constant:
If specified, this value overrides the value of
MaxInFlightMessagesConstant. This number may be negative.

was390_throttle_scaleFactor:
If specified, this value overrides the value of
MaxInFlightMessagesScaleFactor This number should be
non-negative.

The fix for this APAR is currently targeted for inclusion in
fix packs 8.5.5.13 and 9.0.0.6.  Please refer to the
Recommended Updates page for delivery information:
http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980

Temporary fix

Comments

APAR Information

APAR number
PI80377
Reported component name
WEBSPHERE FOR Z
Reported component ID
5655I3500
Reported release
850
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt / Xsystem
Submitted date
2017-04-21
Closed date
2017-07-27
Last modified date
2017-07-27

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

Fix information

Fixed component name
WEBSPHERE FOR Z
Fixed component ID
5655I3500

Applicable component levels

R850 PSY
UP

[{"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Product":{"code":"SS7K4U","label":"WebSphere Application Server for z\/OS"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"850","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
03 May 2022

Tips

PI80377: NEW ACTIVIATION SPEC PROPERTIES - CONTROL BUILD UP/FLOW OF MDB REQUESTS

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name

Fixed component ID

Applicable component levels

R850 PSY

Document Information

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