PM40158: POOR PERFORMANCE ON REQUESTS WITHOUT AFFINITY DURING HEAVY LOAD

Fixes are available

APAR status

Closed as program error.

Error description

By default, WebSphere sets the WLM select policy to 1, which
forces WLM to select work requests with affinity to a servant
over those without affinity.  As the load on a server rises,
and a large number of requests with affinity flow into a server,
this can cause a severe performance degradation on requests
without affinity.  Customers experiencing this problem will
find very long request runtimes for requests without affinity
(i.e. requests that do not have an HTTP session) in a review of
performance data for the server.  A deeper review of these
requests will show that most of the wait time was spent waiting
for WLM to route the request.

Local fix

Problem summary

****************************************************************
* USERS AFFECTED:  All users of IBM WebSphere Application      *
*                  Server V7.0                                 *
****************************************************************
* PROBLEM DESCRIPTION: A WebSphere Application Server for      *
*                      z/OS                                    *
*                      server experiences slower response      *
*                      time                                    *
*                      for requests that have no established   *
*                      affinity to a Servant.                  *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
WebSphere creates a WLM dynamic application environment that is
used for selecting work from the WLM queue.  One of the
parameters that is passed to WLM is the SELECT_POLICY, and the
default value that WebSphere uses causes WLM to select work
targetted to a specific Servant prior to selecting work that
has
no affinity.  This SELECT_POLICY is perfectly valid and is
appropriate in many cases, however in certain specific cases
an administrator may want to use a different option.
Currently,
WebSphere does not allow the SELECT_POLICY to be overridden.

Problem conclusion

A new property, dynapplenv_wlm_select_policy, was added.  The
value supplied is passed directly to WLM as the SELECT_POLICY
of the IWMAEDEF service used to create the dynamic application
environment.

APAR PM40158 APAR requires changes to documentation.

NOTE: Periodically, we refresh the documentation on our
Web site, so the changes might have been made before you
read this text. To access the latest on-line
documentation, go to the product library page at:

http://www.ibm.com/software/webservers/appserv/library

The following changes to the z/OS version of the WebSphere
Application Server Version 7.0 Information Center will be
made available in September, 2011.

The topic "Application server custom properties for z/OS"
will be updated to include the following description of
the new dynapplenv_wlm_select_policy environment
variable:

dynapplenv_wlm_select_policy

Specifies that value that you want passed to the z/OS
Workload Manager (WLM) as the SELECT_POLICY parameter of
the IWMAEDEF service.

The IWMAEDEF service is used to create the dynamic
application environment for the selection of work from the
WLM queue. For more information about this service, see the
z/OS WLM documentation for your version of the z/OS
operating system.

You can specify values of 0, 1 or 2 for this property.

- If you specify a value of 0, the oldest request on either
the service class or server address space queue is
selected first.
- If you specify a value of 1, any requests on the server
address space queue are always selected first.
- If you specify a value of 2, any requests on the service
class queue are always selected first.

Data Type  Integer
Default  1
Used by Daemon  No

APAR PM40158 is currently targeted for inclusion in
Service Level (Fix Pack) 7.0.0.19 of WebSphere
Application Server V7.0 and Fix Pack 8.0.0.1 of WebSphere
application Sever V8.0.

Please refer to URL:
//www.ibm.com/support/docview.wss?rs=404&uid=swg27006970
for Fix Pack availability.

Temporary fix

Comments

APAR Information

APAR number
PM40158
Reported component name
WEBSPHERE FOR Z
Reported component ID
5655I3500
Reported release
700
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2011-05-26
Closed date
2011-07-15
Last modified date
2011-10-04

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

R700 PSY UK71297
UP11/09/10 P F109

Fix is available

Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.

[{"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":"7.0","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
27 October 2021

Tips

PM40158: POOR PERFORMANCE ON REQUESTS WITHOUT AFFINITY DURING HEAVY LOAD

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

R700 PSY UK71297

Fix is available

Select the PTF appropriate for your component level. You will be required to sign in. Distribution on physical media is not available in all countries.

Document Information

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