REXX External Assembler API › Environmental Considerations

Environmental Considerations

In the TSO/E implementation of REXX, each user has their own address space. While (say, under ISPF), there may be more than one REXX process or task executing at the same time, the entire address space and all its resources are private to that user.

Under TSO/E, most programs execute unauthorized. The programs are loaded from non-authorized libraries, and cannot perform authorized functions. A program cannot do damage to system data areas.

Under Tivoli NetView, multiple users share the one address space. Work for different users is processed under different tasks. Also, the address space itself and all tasks in the address space execute in an APF-authorized environment.

Under CA NetMaster, multiple users share one address space, and the environment is APF-authorized. The ramifications of this, when writing REXX external interface programs, include the following:

• All programs must be loaded from an APF-authorized library. APF libraries are generally restricted for update by the security system.
• The interface programs can perform functions that may damage the address space or system. Thus it is imperative that they are carefully checked.
• User-written external interface programs must be registered before they can be used. This additional step prevents accidental execution of programs in an APF-authorized environment.
• It is a good idea to restrict update access to the REXX source libraries available to a region.