Serial handle sharing between threads, without call blocking. If a thread tries to use a handle that is already in use by another thread, the call blocks (waits) until the handle becomes available. However, only one thread at a time can use any particular handle, that is, only serial use of a handle is permitted. This option indicates that connection and object handles allocated by one thread of a process can be used by other threads belonging to the same process. Serial handle sharing between threads, with call blocking. The handles cannot be used by other threads belonging to the same process. This option indicates that connection and object handles can be used only by the thread that caused the handle to be allocated (that is, the thread that issued the MQCONN, MQCONNX, or MQOPEN call). These options are supported in the following environments: AIX, HP-UX, OS/400, Solaris, Linux, Windows. Only one of these options can be specified. Handle-sharing options: The following options control the sharing of handles between different threads (units of parallel processing) within the same process.

See the MQCONNX documentation in the Application Programming Reference guide under MQ 5.3. The handle sharing options allow a call to either block (wait) until the other call completes, or fail with an MQRC_CALL_IN_PROGRESS return code. And that is still with the restriction of only one call outstanding at any one time. I'm only aware of being able to share an HCONN value across threads in MQ 5.3.

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