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IMS Stays Fit After 40

Avoiding storage failures with OTMA

Avoiding storage failures with OTMA

If your Information Management System (IMS) handles a moderate to heavy transaction load through the IMS Open Transaction Manager Access (OTMA) and something were to delay processing in IMS temporarily, the storage OTMA needs to keep track of all the transactions waiting to be processed could increase significantly. In the worst-case scenario, a flood of transaction messages for OTMA can exhaust z/OS storage below the 16 MB line and bring IMS down with an S40D or S878 abend. If that happens, you’ll likely need to do an initial program load to get IMS going again, in which case, all of your other z/OS subsystems on the LPAR would come down, too.

Sound scary? It is, but recent enhancements in both IMS 10 and 11 can help minimize the impact of a flood condition and speed the return to normal processing. Most importantly, some of these enhancements can help you prevent a message flood condition and any related catastrophic storage failure in the first place. These enhancements include:

  • OTMA flood monitoring and notification
  • OTMA control over the number of transaction messages in IMS
  • OTMA control over the number of OTMA transaction pipes (tpipes) in IMS
  • Improved timeout controls for OTMA messages and IMS transactions (the IMS transaction option is in version 11 only)

Some of these enhancements address the flood risk more directly than others, but all of them can help.

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 bpj@us.ibm.com.

Dave Cameron is a senior software engineer for IMS development. He can be contacted at daveac@ca.ibm.com.

Jack Yuan is a senior software engineer for IMS development. He can be contacted at jackyuan@us.ibm.com



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