In z/OS, the typical and most familiar implementation of REXX is the TSO/E REXX interpreter. This interpreter is also used in other IBM products and environments such as Tivoli NetView.
The REXX implementation used in CA NetMaster is called NetMaster REXX. It uses a REXX engine called GREXX. GREXX is a REXX implementation written by CA.
GREXX is a compiled implementation of REXX. Because GREXX compiles rather than interprets source, there are differences between the GREXX and TSO/E implementations of REXX. The differences and similarities are covered in detail in this chapter.