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IMS Performance Team Puts Communications Capabilities to the Test

Editor’s note: This is the second of two articles on IMS-to-IMS communication via TCP/IP. Part one, “Making a Better Connection,” introduced the capability available in IMS version 12 and how it works.

As outlined in part 1, the IBM Information Management System (IMS) version 12 introduces support for TCP/IP communications between two geographically remote IMSs. The IBM IMS Performance team conducted tests to establish performance benchmarks for open transaction manager access (OTMA) messages transmitted between two IMSs using IMS-to-IMS TCP/IP communication.

The tests were performed in a sysplex with two IMSs, each on a separate LPAR on an IBM System z10 Enterprise Class mainframe. During testing, application programs running in 132 dependent regions in one IMS sent 12 transaction messages to another IMS via OTMA over an IMS-to-IMS TCP/IP connection.

In the sending system, the transaction messages were distributed across 120 OTMA destination descriptors. In the receiving system, application programs running in another 132 dependent regions retrieved the transaction messages from the input queue. The transactions were defined in the receiving IMS as non-response mode transactions.

The test was run in two scenarios: one in which the sending IMS Connect was configured with only one TCP/IP connection to the receiving IMS Connect; and another in which the sending IMS Connect was configured with 12 TCP/IP connections to the receiving IMS Connect. Except for the changes required to the OTMA destination descriptors to recognize the additional TCP/IP connections, all other aspects of the two scenarios were the same.

The 12-connection scenario recorded a peak transmission rate of 9,500 messages per second, 6 percent more per second than the single-connection scenario, which still recorded 9,014 messages per second. When measured in CPU processing time, the 12-connection scenario recorded a peak transmission rate of 11,815 messages per second of CPU time, 13 percent more than the single-connection scenario, which recorded 10,481.

For more on the testing conducted, see the “Testing Environment Details” sidebar.

Ben Johnson is an IBM information developer. He has been writing about IMS since 2003, focusing on both IMS database administration and IMS communications and connections, with a particular interest in OTMA and IMS Connect. He can be contacted at

Dave Cameron is a senior software engineer for IMS development. He can be contacted at

Jack Yuan is a senior software engineer for IMS development. He can be contacted at

Yu Ying Wang is an advisory software engineer for IMS performance test. She can be contacted at



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