Invoking Callable Services

Most z/VM® routines are stored in a callable services library (CSL). When a program contains a call to a CSL routine, the call is not resolved until the program is run and the call is made (as opposed to when the module is built).

Note: For general information about CMS programming interfaces, see the z/VM: CMS Application Development Guide.

z/VM comes with two callable services libraries:

  • VMLIB contains routines that:
    • Call CMS file system management functions (CMS file pool and minidisk I/O)
    • Call CMS file pool administration functions
    • Access the current generation of REXX variables
    • Issue VM commands through a REXX exec
    • Call the CMS Extract/Replace facility, which enables application programs to obtain or modify selected system information without release or VM system dependencies
    • Manipulate the CMS program stack
    • Use the CMS Coordinated Resource Recovery (CRR) facility to maintain data integrity
    • Use VM data spaces
    • Call program-to-program communications functions using Common Programming Interface (CPI) Communications
    • Call CPI resource recovery functions
    • Provide CMS file pool exits
    • Determine if the routine is called from within the XEDIT environment

    This book describes the VMLIB routines in detail, except those for file pool exits, CPI Communications, and CPI resource recovery. The file pool exit routines are described in z/VM: CMS File Pool Planning, Administration, and Operation.

    CPI Communications and CPI Resource Recovery Routines

    Application programs must call CPI Communications and CPI resource recovery routines in a way that is different from other VMLIB routines.

    Routines that perform CPI Communications functions are documented in the Common Programming Interface Communications Reference. This includes common routines that can be used across various IBM systems, as well as VM extension routines.

    Routines that perform CPI resource recovery functions are documented in the Common Programming Interface Resource Recovery Reference.

    In addition, the z/VM: CMS Application Development Guide gives an overview of writing communications programs in VM, while z/VM: CP Programming Services provides additional reference information.
  • VMMTLIB contains routines that:
    • Call CMS application multitasking functions
    • Call OpenExtensions (POSIX) services
    • Get the value set for the workstation display address

    The CMS application multitasking routines are described in z/VM: CMS Application Multitasking. The routines for calling OpenExtensions services are described in the z/VM: OpenExtensions Callable Services Reference. The WorkstationGetAddress routine is described in this book.

DFSMS/VM provides two additional callable services libraries:
  • FSMPPSI contains Removable Media Services (RMS) Tape Library Dataserver interface routines. These routines allow applications running under CMS OS simulation to issue requests for Tape Library Dataserver functions such as mounting or demounting a tape, querying library information, setting or resetting the device category, and setting the volume category. The routines are described in z/VM: DFSMS/VM Removable Media Services.
  • FSMPSI contains DFSMS/VM installation-wide exit routines. These exits allow you to customize DFSMS/VM functions such as accounting records, authorization checking, migration and erasure verification, selecting the real device, authorized request pre-verification and post-verification, verifying shared resources, and issuing commands for device attachment and detachment. The routines are described in z/VM: DFSMS/VM Customization.