CICS function shipping environment

This topic describes the system entries for function shipping in the terminal control table, and how function shipping requests or replies are transformed between the format suitable for transmission and the internal parameter list format.

System entries in the terminal control table

All remote systems with which a given system is able to communicate are identified and described in terminal control table system entries (TCTSEs). The name of the system entry is the name specified in the SYSIDNT field of the CICS® table entry describing a remote resource.

CICS uses the TCTSE as an anchor point to queue requests made by CICS transactions for connection to the remote system.

Figure 1 shows three TCTTEs. If a transaction fails and you get a transaction dump, this figure shows you how to find the relevant TCTTEs from the TCA.
Figure 1. Task's view of CICS function shipping TCTTEs
Diagram illustrating demonstrating how to find TCTTEs from a TCA.

Transformation of requests and replies for transmission between systems

Before a request or reply can be transmitted, it must be transformed from its internal, parameter list (EXEC interface) format to a format suitable for transmission; when received after transmission, the request must be transformed back into a parameter list format.

There are four such transformations (numbered 1 through 4), which are performed by DFHXFP, or by DFHXFX if optimized data transformations are possible. The latter applies only to data transformations for function shipping in an MRO environment, excluding those relating to DL/I requests.

Transformation 1
For a request to be sent by the originating system; transforms from parameter list format to transmission format.
Transformation 2
For a request received by the mirror transaction; transforms from transmission format to parameter list format.
Transformation 3
For a reply to be sent by the mirror transaction; transforms from parameter list format to transmission format.
Transformation 4
For a reply received by the originating system; transforms from transmission format to parameter list format.

The parameter list format refers to the parameter list that is normally passed to DFHEIP (for CICS requests) or to DFHDLI (for DL/I requests).

The transmission formats of these requests and replies (excluding those for sync point protocol) are described in the DFHFMHDS DSECT.

Information that DFHXFP and DFHXFX must retain between transformations 1 and 4 (in the originating system) or between transformations 2 and 3 (in the mirror system) is stored in a transformer storage area called XFRDS. See XFR - Function shipping request control block for a detailed description of this control block.