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Trying to document a weird condition in CICS


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John Poulakos

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Joined: 13 Jun 2012
Posts: 180
Location: United States

PostPosted: Fri Aug 30, 2019 11:19 pm
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I have an condition that causes a user to get locked out of CICS. It doesn't happen very often and I know how to correct it. But, I need to document what causes it and I am having a hard time with that.

The symptoms are a user is prevented from accessing CICS because they are already signed on at a different terminal. They could stay in this state until CICS is restarted, if I did not intervene. I can identify the user in the CICS tables, find the task that is being held and kill the task or terminal. No other users are impacted.

When I kill the task (or terminal) I get an abend and dump that shows the transaction is in a DB2 program and I can tell it is running under the Open API TCB (L8) as a TRUE exit. All of our CICS transactions are Psuedo-conversational, so there is no way it could have returned a screen and held on to the terminal session. There is no evidence of LOSTERM exit being driven, so the user did not break the connection before getting a response.

The only conclusion I can draw is the TCB either never got posted or it was posted under the wrong key. I can't come up with a good reason for why or how this could happen.
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John Poulakos

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Joined: 13 Jun 2012
Posts: 180
Location: United States

PostPosted: Fri Dec 06, 2019 8:43 pm
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I determined the problem was caused by a recursive error in DB2. When this occurs, the enclave backward chain is broken and DB2 posts completion under the wrong storage key. (See CICS TRUE exit). The fix is to kill the task.
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