PostOnlineCommand and PreOfflineCommand in MSCS

Use these commands to integrate IBM MQ MSCS support with other systems. We can use them to issue IBM MQ commands, wih some restrictions.

Specify these commands in the Parameters to a resource of type IBM MQ MSCS. We can use them to integrate IBM MQ MSCS support with other systems or procedures. For example, you could specify the name of a program that sends a mail message, activates a pager, or generates some other form of alert to be captured by another monitoring system.

PostOnlineCommand is invoked when the resource changes from offline to online; PreOfflineCommand is invoked for a change from online to offline. When invoked these commands are run, by default, from the Windows system directory. Because IBM MQ uses a 32-bit resource monitor process, on Windows 64-bit systems, this is the \Windows\SysWOW64 directory rather than the \Windows\system32 directory. For more information, see the Microsoft documentation about file redirection in a Windows x64 environment. Both commands run under the user account used to run the MSCS Cluster Service; and are invoked asynchronously; IBM MQ MSCS support does not wait for them to complete before continuing. This eliminates any risk that they might block or delay further cluster operations.

We can also use these commands to issue IBM MQ commands, for example to restart Requester channels. However, the commands are run at the point in time when the queue manager's state changes so they are not intended to perform long-running functions and must not make assumptions about the current state of the queue manager; it is quite possible that, immediately after the queue manager was brought online, an administrator issued an offline command.

To run programs that depend on the state of the queue manager, consider creating instances of the MSCS Generic Application resource type, placing them in the same MSCS group as the queue manager resource, and making them dependent on the queue manager resource.