[Version 5.0.2 and later]Configuring an application server to use the WLM even distribution of HTTP requests function

Normally an application server is configured for servant region affinity, and HTTP session objects reside in one or two servant regions. If you want HTTP requests more evenly distributed to the servant regions in your configuration, you can configure an application server to use the workload management (WLM) even distribution of HTTP requests function. When an application server uses the WLM even distribution function, HTTP requests, for which affinity has not yet been established, are evenly distributed, in a round-robin manner, to all of the servant regions in your configuration.

Before you begin

Your application server should be running on a z/OS system that is at Version 1.4 or later. Because you are distributing HTTP requests among multiple servant regions in this task, you should also have multiple servant regions enabled to use this function. See Enabling multiple servant regions for more information.

Why and when to perform this task

Use this task if your application server is experiencing problems with the default workload distribution strategy. The default workload distribution strategy uses a hot servant region for running requests that create HTTP session objects. Consider configuring WebSphere Application Server and the z/OS Workload Manager to distribute HTTP requests, for which affinity has not been established:For more background about when to use this task, see WLM even distribution of HTTP requests.

Steps for this task

  1. Add the wlm_stateful_session_placement_on WebSphere variable for your application server configuration settings.
    1. Click Environment > Manage WebSphere variables, and select the server for which you want to use the WLM even distribution of HTTP requests function.
    2. Click New.
    3. Add a new variable with wlm_stateful_session_placement_on for name and 1 for value.
    4. Click Apply and then click Save and Synchronize to update your changes.
  2. Set the optimal minimum and maximum number of servant regions for the workload.
    Set the minimum and maximum number of servant regions to handle the expected number of HTTP sessions with affinity. The minimum number of servant regions should be greater than one.
    If, for example, you expect 15,000 HTTP session objects are established in the server during the day, then you might set the minimum number of servants to some value larger than one. The minimum of servant regions is dependent upon the size and number of the HTTP session objects. However, the initial arrival rate of client requests establishing the affinity, the frequency of client interaction, the duration of each client interaction (CPU time and thread occupancy time), and the length of time that the HTTP session object is maintained also need to be considered when establishing the minimum value for the number of servant regions.
    1. To set the number of servant regions, click Servers > Application servers > server_name > Server instance.
    2. Set the minimum and maximum number of servant regions.
    3. Click Save and synchronize to apply the changes.
  3. If you have set up your classification mapping file to specify more than one transaction class on a mapping rule for WebSphere Application Server managed round robin support, you should remove this section from your classification mapping file.
    For example, if you have a line in your classification mapping file like the following:
    TransClassMap *:8080 /Dynacache1Web1/Servlet1 TCLASS1 TCLASS2 TCLASS3
    Modify this line of the classification mapping file to have only one transaction class, like the following example:
    TransClassMap *:8080 /Dynacache1Web1/Servlet1 TCLASS1
    You also must update the z/OS workload manager policy to remove the extra service classes that were only necessary to get WebSphere Application Server managed round robin support. Following is an example of removing the extra service classes:
      Subsystem-Type  Xref  Notes  Options  Help                                 
     --------------------------------------------------------------------------   
                      Modify Rules for the Subsystem Type     Row 9 to 16 of 16   
     Command ===> ____________________________________________ SCROLL ===> CSR    
                                                                                  
     Subsystem Type . : CB          Fold qualifier names?   Y  (Y or N)           
     Description  . . . Component Broker requests                                 
                                                                                  
     Action codes:   A=After     C=Copy        M=Move     I=Insert rule           
                     B=Before    D=Delete row  R=Repeat   IS=Insert Sub-rule      
                                                                  More ===>       
               --------Qualifier--------               -------Class--------       
     Action    Type       Name     Start                Service     Report        
                                              DEFAULTS: AZAMS1      RBBDEFLT      
      ____  1  CN         AZSR01   ___                  AZAMS1      RAZAMS1       
      ____  2    TC         TCLASS1  ___                AZAMS1      RAZAMS1       
      _d__  2    TC         TCLASS2  ___                AZAMS2      RAZAMS1       
      _d__  2    TC         TCLASS3  ___                AZAMS3      RAZAMS1       
      ____  1  CN         AZSR02   ___                  AZAMS2      RAZAMS2       
      ____  1  CN         AZSR02   ___                  AZAMS3      RAZAMS3       
    ****************************** BOTTOM OF DATA ****************************** 
  4. Restart the server.
    The server recognizes the wlm_stateful_session_placement_on variable after it is restarted.

Results

The application server uses the WLM even distribution of HTTP requests function to handle its workload instead of showing affinity to a certain servant region.

What to do next

See Detecting and handling problems with run-time components to handle problems with server clusters and workloads.

Related concepts
Workload management (WLM)
WLM even distribution of HTTP requests



Searchable topic ID:   trun_wlm_sessionplacement
Last updated: Jun 21, 2007 9:56:50 PM CDT    WebSphere Application Server for z/OS, Version 5.0.2
http://publib.boulder.ibm.com/infocenter/wasinfo/index.jsp?topic=/com.ibm.websphere.zseries.doc/info/zseries/ae/trun_wlm_sessionplacement.html

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