Common dump queue configurations

In a standard HSMplex configuration, all hosts are connected to the same common dump queue (CDQ) and all hosts are eligible to process dumps regardless of which host was used to submit the requests. The CDQ is a queue of dump requests that is shared by these host, managed by a master scheduler (MS) host and implemented through the use of the cross-system coupling facility (XCF) for host-to-host communication between an XCF defined group and its members. The purpose of the CDQ is to balance dump processing across the resources available in all the hosts and return results back to the host where the request originated to post the user complete.

As illustrated in Figure 1, the CDQ group allows for flexible configurations. This provides the capability to:
  • Define multiple queues in the same HSMplex
  • Allow group members to both receive and process requests, only process requests, or only receive requests.
Figure 1. CDQ -- Flexible Configurations
The CDQ group allows for flexible configurations of one or more DFSMShsm hosts.

Results are returned to the submitting host, but progress and status messages are recorded on the processing host, that is, the host processing the request.

The DFSMShsm host types are:

Submitting host
Receives requests from commands and sends it to the master scheduler host. When the command is completed by the group, the submitting host is notified to post the user that the command has completed.
Master scheduler (MS)
Is the DFSMShsm host that manages all of the dump requests in the CDQ. It accepts requests from a submitting host and from itself. The master scheduler assigns the requests to eligible hosts (processing hosts), including itself, that have available tasks to process the work, while balancing the utilization of the dump tasks in the group. The master scheduler also manages the interaction between the processing host for stacking and the submitting host for the command complete notifications.
Processing host
Receives assigned work requests from the master scheduler, completes the work, and interacts with the master scheduler to manage stacking

Any host in the CDQ could be any or all of the host types depending on your environment.

If you do not want dump tasks on a host to be used by the CDQ group, avoid using HOLD DUMP. Instead use SETSYS MAXDUMPTASKS(0) to prevent the host's dump tasks from being used. This has the same effect as HOLD DUMP without the risk of affecting master scheduler responsibilities. HOLD DUMP from the master scheduler prevents it from assigning and processing requests for the CDQ.