Concurrent Requests and Commands

SA z/OS handles concurrent requests and commands differently:

• If two or more requests arrive for the same subsystem from different controllers, the first request is processed but the second and subsequent requests fail until the first request has completed processing. There is no attempt to queue the requests; each request is processed as soon as it is received. An existing outstanding request will prevent new requests from being processed and will post a completion code of U005.
• If two or more commands arrive for the same subsystem from different controllers, SA z/OS attempts to execute them simultaneously. This may result in one of the commands being timed out due to not reaching its desired status for the subsystem. It is possible that both commands require the same desired status, and in such cases both commands will probably succeed.

  It is not possible to serialize commands for the same resource because the command text is free form. In addition there may be intersections that result in command conflicts. For example, if one command stops a parent and another starts a child. The system relies on the timeout function to resolve these situations and will as a result report one of the commands in error.

Note that creating TWS operations with the same workstation, ADID, operation number and job name might result in unpredictable effects. This is because when SA z/OS posts the result of the operation, all operations with the same ID on all active controllers will also be posted.To avoid this, you should ensure that the ADID (Application Identification) is unique.

The ACF $$$OPCA DOMAINID entry, which is defined in the OPC Workstation Domains policy object in the customization dialog panels, must specify workstations for all active controllers. An installation can either use the same workstation names for different active controllers or it can specify different names that resolve to the same set of domain IDs. For example, active controller 1 might use NV11 for domain ID IPSFM, and active controller 2 might use NV21 for the same domain ID. This is however limited because the first two characters of the workstation name must be NV.