Accessing the command-level parameter structure from exits XICEREQ, XICERES, and XICEREQC

The command-level parameter structure consists of a series of addresses. The first address points to the EXEC interface descriptor (EID), which consists of a 9-byte area that describes the type of request and identifies each keyword specified with the request. The remaining addresses point to pieces of data associated with the request. For example, the second address points to the interval for START requests. You can examine the EID to determine the type of request and the keywords specified. You can examine the other parameters in the list to determine the values of the keywords. You can also modify values of keywords specified on the request. For example, you could change the SYSID specified in the request.

Figure 1. The command-level parameter structure for interval control
The picture shows, using a series of interconnected boxes, the relationships between the fields in the command-level parameter structure. The command-level parameter structure, and the relationships between its fields, are fully described in the text following the picture.

End of parameter list indicator

The high-order bit is set on in the last address set in the parameter list to indicate that it is the last one in the list. On return from your user exit program, CICS® scans the parameter list for the high-order bit to find the last parameter. Therefore, if you modify the length of the parameter list, you must also reset the high-order bit to indicate which is the new last address.

For example, if the parameter list specifies only the first four addresses (IC_ADDR0, the address of the EID, to IC_ADDR3, the address of the name of the transaction named in a START request), the high-order bit is set on in IPC_ADDR3. If you extend the parameter list by setting the address of a SYSID in IC_ADDR7, you must unset the high-order bit in IC_ADDR3 and set it on in IC_ADDR7 instead.

The maximum size of parameter list is supplied to the exit, thus allowing your exit program to add any parameters not already specified without needing to first obtain more storage.

The original parameter list, as it was before XICEREQ was invoked, is restored after the completion of XICEREQC. It follows that the execution diagnostic facility (EDF) displays the original command before and after execution: EDF does not display any changes made by the exit.