CMS Services Available to the Alternate Exec Processor

In addition to the standard services provided by CMS, alternate exec processors have access to the following CMS services:
  • Terminal input buffer line count. See the z/VM: REXX/VM User's Guide for more information.
  • Disk block size determination. You can obtain this information using the Extract/Replace facility. See the z/VM: CMS Callable Services Reference for more information.
  • The non-SVC subcommand invocation that uses a minimum overhead subcommand call for issuing commands. See the z/VM: REXX/VM Reference for more information.
  • The CMS global exit facility and the REXEXIT macroinstruction. See the z/VM: CMS Macros and Functions Reference for more information.
  • Recursion control when using the CMS subcommand interface.
    • If you want to inhibit the recursion of execs, the fourth word of the extended plist must be nonzero. It must be the address of a CSFCB containing a pointer to the 8-byte name of the current exec.
    • If you do not want to inhibit the recursion of exec, the fourth word of the extended plist must be zero (that is, there is no CSFCB).
    See the z/VM: REXX/VM Reference for information on CMS command search order and how it effects calling execs recursively.
  • CMS ensures that on entry to any alternate exec processor, both tokenized and extended plists are available. When generating calls to other commands or execs, an alternate exec processor must provide a tokenized plist and optionally provide an extended plist. It must also set the user call-type information to indicate the format of the plists provided. See the z/VM: CMS Application Development Guide for Assembler for more information about creating and passing plists.

    If only a tokenized plist is available, the CMS EXEC interface generates an extended plist from information in the tokenized plist, before invoking the language processor of the called exec.

    Note: Although an alternate exec processor can execute above the 16 MB line, when generating calls to an exec written in EXEC 2 or CMS EXEC language, an alternate exec processor must ensure that the parameter lists and the data referenced by the parameter lists reside below the 16 MB line.