The ISSUE PREPARE command

The ISSUE PREPARE (GDS ISSUE PREPARE for the APPC basic interface) command is used to send the initial syncpoint flow to a selected partner on an APPC conversation at sync level 2. Depending on the partner’s response, this command can then be followed by a SYNCPOINT or SYNCPOINT ROLLBACK command.

The reasons for using ISSUE PREPARE are as follows:

1. In complex DTP involving several conversing transactions, an ISSUE ERROR command from one of the transactions may not reach the syncpoint initiator in time to prevent it from issuing a SYNCPOINT command. This can lead to complex backout procedures for the distributed unit of work.

   Use ISSUE PREPARE as a way of flushing any error responses from the network.

2. If one or more syncpoint agents are not completely “reliable”, use ISSUE PREPARE to check the status of these agents before proceeding with a general distributed syncpoint.

   Receiving ISSUE PREPARE is exactly the same as receiving SYNCPOINT. The partner program cannot detect any difference.