You can also define a timeout interval for synchronous callout requests on the OTMA destination descriptor. If the timeout value specified on the OTMA destination descriptor differs from the timeout value specified on the ICAL call, IMS uses the smaller of the two values. In IMS Version 11, you can use the online IMS commands CREATE OTMADESC or UPDATE OTMADESC to update or add OTMA destination descriptors without taking IMS offline.

Testing Support for IMS Synchronous Callout Configurations

DFSDDLT0 is an IMS application program delivered with IMS for use as a testing tool. DFSDDLT0 issues DL/I calls, including ICAL, to IMS based on control statement information. Figure 2 shows how to send a synchronous callout request message to a destination named OTMDEST1. The request contains 100 bytes of data; the response is also expected to contain 100 bytes of data. A timeout value of 500 (5 seconds) is specified.


Enhancements for Synchronous Callout Support

If OTMA receives a positive acknowledgment (ACK) for a synchronous callout request from the external provider after the timeout interval for receiving a response has expired, IMS rejects the ACK and returns sense code X’2B’ to the OTMA client to indicate the reason. The handling of ACK and response messages was further improved in IMS Version 10 APAR PM14872.

IMS Version 11 provides another ACK timeout function for even finer control over how IMS handles late acknowledgments from the external data or service provider. To be effective, the ACK timeout interval must be shorter than the response timeout interval.

For improved availability, you can now configure multiple external applications or Web services to process the callout requests IMS issues to one destination. If one of the external applications or Web services fails, others can continue to process callout requests from IMS.

A new sample COBOL application program, DFSSCBL, was added as part of the IMS Installation Verification Program (IVP). It’s useful for verifying the correct configuration of the IMS synchronous callout support and for illustrating use of the ICAL DLI call. The DFSSCBL sample ships in the IMS.SDFSSMPL data set.

The IMS Monitor can now collect data related to the ICAL DLI call and display the data in the CALL SUMMARY report the IMS Monitor Report Print utility (DFSUTR20) creates.

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