REXX/CICS supports the ability for users to write new REXX/CICS commands in REXX. These commands do not function as nested REXX execs, and unlike nested REXX execs have the ability to get and set the values of REXX variables in the user exec that issued the command. Therefore, commands written in REXX can have similar capabilities as commands written in Assembler or other languages. Also, commands can be quickly written in REXX to speed systems development (in a building block structure), and then can selectively be rewritten in Assembler (or any other CICS supported language) at a later date, if performance requirements dictate.