The command-level parameter structure

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 bit string 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.

End of parameter list indicator

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.

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.