This Loop is Not so Transient
ByronBaldwin 06000099ST Visits (2289)
There are a number of different examples of loops we encounter on a daily basis which are beneficial to our everyday lives (traffic circles, musical loops, shoe laces). But the type of loop I want to discuss today causes your CICS Transaction Server for z/OS (CICS TS) region to become inoperative which may lead to some unhappy users. In this particular blog entry I will walk you through how and why this problem occurs and the solutions to alleviate this in your CICS environment.
The problem is triggered with PTF UK63439 (APAR PM24620) for CICS TS 3.2 installed and using a non-recoverable intrapartition Transient Data Queue (TDQ) defined with the following attributes:
ATIFACILITY = terminal
FACILITYID = (LU62 parallel connection)
When CICS attempts to read the aforementioned defined TDQ this is where the problem begins and does not end until the region is shutdown. CICS starts to loop attaching Transient Data Trigger task with the Automatic Transaction Initiation (ATI) process, as DFHALP did not take into consideration that AIDSTTSK had different meaning for AIDTYPE = AIDTDP.
This problem was introduced by code added by CICS TS 3.2 APAR PM24620 which did not take into account this type of TDQ.
NOTE: The same code was added by APAR PM27536 (UK63430) for CICS TS 4.1 and is included in the base code of CICS TS 4.2.
To address this issue, the following APARs have been opened for the different releases of CICS:
At the time of this blog entry the CICS TS 4.2 APAR is currently open and the PTF is not available (you can click on the APAR link above to see the current status of the APAR). But there are two known workarounds for this issue:
As always I would love to hear your feedback concerning this blog. If you have topics you would like to hear about please feel free to advise as well and I will do my best to accommodate the request.
As always DO IT JUST FOR CICS!!!