Contention on CA Dispatch archive and extract subtasks

Document ID : KB000091704
Last Modified Date : 16/04/2018
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Introduction:
Twice now we've had a problem with external archive on "DISPTEST" and external archive on DISPPROD being in contention with each other. Interestingly enough they've both happened at the same time (on DISPPROD and DISPTEST) and both times the only resolution has been to recycle DISPTEST and DISPPROD. We've tried to stop and restart the archive task in both DISPTEST and DISPPROD without success. We have not seen any errors in either of the CA Dispatch started tasks nor in the logs from the external archive subtasks that would justify or explain the reason for the contention. 
Question:
Is there a way to prevent the external subtasks of CA Dispatch from being in contention with each other? 
Environment:
z/os 
 
Answer:
If your site uses products like MIMS or GRS and you run multiple CA Dispatch regions, the ENQs that are used by CA Dispatch for subtask control should be coded into your ENQ management product's “exclusion” list variables.

CA Dispatch makes use of many ENQs to ensure proper task control. The resource being controlled in this case is a task, NOT a data set. For every external task that is started, an ENQ conflict indeed occurs. This is a normal condition and is NOT an indication of a performance problem.
 
The following ENQs are used for task control:
 
 QNAME    RNAME          TASK
 DSA1ACT  CVNO##SVCNO### ARCH1
 DSA2ACT  CVNO##SVCNO### ARCH2
 DSA3ACT  CVNO##SVCNO### ARCH3
 DSA1REQ  CVNO##SVCNO### ARCH1
 DSA2REQ  CVNO##SVCNO### ARCH2
 DSA3REQ  CVNO##SVCNO### ARCH3
 DSEXACT  CVNO##SVCNO### EXTRACT
 DSEXREQ  CVNO##SVCNO### EXTRACT
 userid   CVNO##SVCNO### PC
 ACIFRDR  CVNO##SVCNO### ACIF
 
If conflicts occur with these database access ENQs, check the appropriate database files for I/O contention. 
The RNAME is unique for each CA Dispatch system and these ENQs need not be propagated across systems using GRS or other software.
                        
Notes: 
- CA Dispatch does not issue RESERVEs. 
- If your site uses products like MIMS or GRS and you run multiple CA Dispatch regions, the ENQs listed above should be coded into your ENQ management product's “exclusion” list variables. 
Additional Information:
CA Dispatch System Programmers Guide, Troubleshooting, ENQ Usage for Task Control