Programming to the Assist module interface

Programs written to the Assist module interface are very similar (in terms of I/O calls) to conventional IMS™ Transaction Manager (TM) MPPs.

To communicate with IMS TM, use the following calls (depending upon programming language) — CBLADLI, PLIADLI, ASMADLI, or CADLI — instead of CBLTDLI, PLITDLI, ASMTDLI, and CADLI, respectively.
Use the same parameters as with the IMS TM counterparts.
The first IMS call to the I/O PCB must be GU. Subsequent IMS calls to the I/O PCB can be GN and/or ISRT (with intervening database calls, as appropriate).
When the transaction is complete, the server program should issue another GU to the I/O PCB to finalize processing of the present message. If the server program receives a bb status code, (indicating another message has been received for that program), it should loop back and process that message. Note that the Assist module will have closed the previous connection and opened a new connection associated with the new message. When the GU returns a QC status code, no more messages have been received for that program and the program should end.
A set of one GU, one or more GN calls, and one or more ISRT calls to the I/O PCB (with intervening database calls, as required) constitute a transaction. The Assist module interprets each GU as the start of a new transaction.
The PURG call cannot be used to indicate end-of-message; the server should not issue PURG calls to the I/O PCB.
The Assist module GU reads the TIM into the I/O area defined in the server program; consequently, the I/O area you define in the server must be at least 56 bytes in length (the length of the TIM).
If the server program attempts to insert more than 32KB, the Assist module flags this as an error by terminating processing and returning a status code of ZZ.