REXX/CICS supports the standard SAA Level 2 built-in function set,
with the following exceptions:
Stream I/O functions are not supported.
The USERID function returns a 1 to 8 character CICS user ID if
the user is signed on. If the CICS user has not signed on and a default
user has been specified for the CICS region (by the CICS Systems Programmer
specifying DFLTUSER in the CICS startup parameters) then that value
is used.
Note: The default user shares REXX File System and REXX
List System directories.
The STORAGE function, that allows a REXX user to display or modify
the virtual storage of the CICS region. This function can only be
successfully invoked from an authorized exec or by an authorized user.