IBM SC33-1683-02 - Manual (Page 194)

PC_BITS2
Two bytes not used by program control.
PC_EIDOPT5
Not used by program control.
PC_EIDOPT6
Indicates whether the request specifies the SYNCONRETURN option. If
it does, X'80' is set.
PC_ADDR1
is the address of an 8-byte area containing the program name from the
PROGRAM parameter.
PC_ADDR2
is the address of the COMMAREA data.
PC_ADDR3
is the address of a 2-byte area containing the length of the COMMAREA, as a
half-word binary value.
PC_ADDR4
is the address of the INPUTMSG data.
PC_ADDR5
is the address of a 2-byte area containing the length of the INPUTMSG, as a
half-word binary value.
PC_ADDR6
is the address of a 2-byte area containing the length specified on the
DATALENGTH parameter, defining how much data is to be sent from the
COMMAREA. The length is held as a half-word binary value.
PC_ADDR7
is the address of the 4-byte name of the remote system the LINK request is to
be shipped to, as specified on the SYSID parameter.
PC_ADDR8
is the address of the 4-byte name of the mirror transaction to be attached in the
remote system, as specified on the TRANSID parameter.
Modifying fields in the command parameter structure
Some fields that are passed to program control are used as input to the request,
some are used as output fields, and some are used for both input and output. The
method your user exit program uses to modify a field depends on the usage of the
field.
Modifying input fields: The correct method of modifying an input field is to create
a new copy of it, and to change the address in the command parameter list to point
to your new data.
Note: You must never modify an input field by altering the data that is pointed to by
the command parameter list. To do so would corrupt storage belonging to the
application program and could cause a failure when the program attempted
to reuse the field.
Modifying output fields: The technique described in “Modifying input fields” is not
suitable for modifying output fields. (The results would be returned to the new area
instead of the application’s area, and would be invisible to the application.)
program control program exits
162 CICS TS for OS/390: CICS Customization Guide