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:
Use ISSUE PREPARE as a way of flushing any error responses from the network.
Receiving ISSUE PREPARE is exactly the same as receiving SYNCPOINT. The partner program cannot detect any difference.