IBM SC33-1683-02 - Manual (Page 438)

program, the program thus invoked executes according to the execution key
(EXECKEY) defined in its program resource definition.
Important
You are strongly recommended to specify EXECKEY(CICS) when defining
both user-replaceable programs and programs to which a user-replaceable
program passes control.
Data storage key for user-replaceable programs
The storage key of storage used by user-replaceable programs depends on how
the storage is obtained:
v The communication area passed to the user-replaceable program by its caller is
always in CICS key.
v Any working storage obtained for the user-replaceable program is in the key set
by the TASKDATAKEY of the transaction under which the program is invoked.
v User-replaceable programs can use EXEC CICS commands to obtain storage, by
issuing:
– Explicit EXEC CICS GETMAIN commands
– Implicit storage requests as a result of EXEC CICS commands that use the
SET option.
The default storage key for storage obtained by EXEC CICS commands is set by
the TASKDATAKEY of the transaction under which the user program is invoked.
As an example, consider a transaction defined with TASKDATAKEY(USER) that
causes a user-replaceable program to be invoked. In this case, any implicit or
explicit storage acquired by the user program by means of an EXEC CICS
command is, by default, in user-key storage. However, on an EXEC CICS
GETMAIN command, the user program can override the TASKDATAKEY option
by specifying either CICSDATAKEY or USERDATAKEY.
notes about user-replaceable programs
406 CICS TS for OS/390: CICS Customization Guide