The Message User Routine

The message user routine for the PRIMARY member receives messages that contain requests for work to be done. The message user routines for the BACKUP and NO-BACKUP members receive messages that contain acknowledgments of work completed or that contain the requested information. The routines determine what has to be done based on the contents of the message control information.

The members of the group have established the following protocol for the use of the message control information (MSGCNTL parameter on IXCMSGOX):

MSGCNTL Contents	Meaning
REQDATA	Request for data.
RETDATA	Return with data.
REQUPD	Request for update.
GOODRC	Confirmation of successful update.
BADRC	Requested update failed.
WORKXFER	The PRIMARY member's status user routine is transferring the work queue to the BACKUP member. (This is the case where the PRIMARY member's status user routine confirms that the member's status update is missing, and the BACKUP member is taking over.)
WORKREQ	The BACKUP member is now the PRIMARY member, and is requesting the work queue from the NO-BACKUP member. (This is the case where XCF assumed a status update missing for the PRIMARY member, indicating that the member's status user routine did not run successfully, and so could not transfer the work queue.)

Based on the contents of the message control information, the message user routine does the following:

If the message control information contains REQDATA or REQUPD, the routine reads in the information from the message buffer, places the request on the DBMGR's work queue, and posts the DBMGR routine.
If the message control information contains RETDATA, the routine reads the information from the message buffer into a pre-established work queue element, and posts a task (the RETINFO task) to return the data to the caller and to notify the requesting member to delete that request from its work queue.
If the message control information contains GOODRC or BADRC, the routine posts the RETINFO task to inform the caller that the requested update was or was not successful.
If the message control information contains WORKXFER, the BACKUP member knows it will be taking over for the PRIMARY. The routine reads in the work queue from the message buffer, placing the queue in storage the routine has obtained. The routine then places the address of the queue into MDATASTR, and posts TASKECB1.
If the message control information contains WORKREQ, it means the following:
- The BACKUP member took over for the PRIMARY member.
- The BACKUP member did not receive the DBMGR's work queue.
- The BACKUP member has to build a new work queue for its DBMGR routine.
NO-BACKUP's message user routine loops through NO-BACKUP's work queue and issues IXCMSGOX to send each element on the queue to the BACKUP member.