checking queue manager status through Visual Basic 6

Question

You should NEVER have to check the QMgr before opening a queue. As I responded to a similar question today, the design proposed is a very, VERY bad design. The effect is to turn async messaging back into synchronous messaging. This couples message producers to consumers, introduces location and resolution dependencies, breaks clustering, defeats WMQ's load distribution and balancing, embeds network topology into the application, and makes the whole system brittle. Please do not blame WMQ for not working correctly after intentionally defeating all its best features except the actual queue/dequeue operations.

If your requestor app is checking that the QMgr is active, you are much better off using a multi-instance connection name and a layer of two or more functionally equivalent QMgrs that can access the cluster. So long as one of the QMgrs is up, the app will cycle between them until it finds one at which to connect.

If your responder app is checking that the QMgr is active, you are much better off just attempting to connect. Responder apps should never fail over to a different QMgr since doing so breaks transactionality and may leave queues unserviced. Instead just ensure that each queue has at least two input handles from local responder apps that do not fail over across QMgrs. (It is OK if the QMgr itself fails over using hardware clustering or multi-instance QMgr though).

If the intent is to check that there's an open input handle on the queue before putting messages there a better design is to have the requesting app not care to which queue instance the messages are routed and instead use the instrumentation built into WMQ to either restart responder apps that lose their input handle, or to disable the queue when nothing's listening.