SA z/OS policy for the SAP Web Dispatcher

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The *SAPSRV add-on policy of SA z/OS 3.5, APAR level OA46166 or higher, contains improved resource definitions for the SAP Web Dispatcher.

  • The SAP Web Dispatcher policy is also based on the standard SAP infrastructure and the SAP start service sapstartsrv to control SAP instances. So a Web Dispatcher instance is controlled via the sapstartsrv framework.
  • In addition to standard system automation mechanisms (Address space monitoring and Process monitoring) to verify that the SAP Web Dispatcher is running, the policy implements and uses the SAP Web Dispatcher health checker mechanism. This mechanism can detect application problems within the SAP Web Dispatcher itself, and initiates a failover if necessary.
  • The health check is implemented in the *SAPSRV add-on policy with a new Web Dispatcher monitoring resource (MTR). This monitoring resource needs a REXX program, which is used to determine the correct health status, either NORMAL or CRITICAL. The REXX program is called SAPWDMTR. This program is delivered with SA z/OS 3.5 and APAR level OA46166 and higher as part of the ING_sap.tar file in the z/OS UNIX directory /usr/lpp/ing/SAP. Add the SAPWDMTR REXX program to a user-defined data set within the NetView command list, for example USER.SINGNREX. These data sets are specified by the DSICLD DD statement of NetView.

SAP Web Dispatcher health checking

A disadvantage of the traditional address space and process monitoring is that it does not receive information if the SAP Web Dispatcher process hangs in a state where it no longer services incoming requests.

In order to handle such a situation, the *SAPSRV add-on policy uses the SAP Web Dispatcher monitoring function wdispmon.

SA z/OS 3.5 APAR OA46166 additionally introduces an enhanced SAP Web Dispatcher automation policy based on the sapstartsrv framework. It uses an enhanced version of:

  • Script start_cs
  • Script checkwd

Both scripts are part of the ING_sap.tar file, which is shipped with SA z/OS in the z/OS UNIX directory /usr/lpp/ing/SAP.

Extract the tar file into the home directory of the SAP administrator user ID such that the SAP Web Dispatcher resource can use them:

/u/<sid>adm

The first script start_cs starts the SAP Web Dispatcher instance. It is used in the STARTUP section of the startup processing for the SAP Web Dispatcher sapstart resource (SAP<SID>WD_ST) in the changed SAP policy.

The second script checkwd implements a monitoring procedure for the SAP Web Dispatcher that relies on the SAP wdispmon function. This script is used in the POSTSTART section of the start-up processing for the SAP Web Dispatcher sapstart resource (SAP<SID>WD_ST) by the changed SAP policy.

For a more detailed description of the scripts, see Reference of the z/OS high availability scripts.