VMS Help V73 Features, System Management Features, Class Scheduler  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    With OpenVMS Version 7.3, there is a new SYSMAN-based interface
    for class scheduling. This new class scheduler, implemented on
    both VAX and Alpha systems, gives you the ability to designate
    the amount of CPU time that a system's users may receive by
    placing the users into scheduling classes. Each class is assigned
    a percentage of the overall system's CPU time. As the system
    runs, the combined set of users in a class are limited to the
    percentage of CPU execution time allocated to their class. The
    users may get some additional CPU time if /windfall is enabled
    for their scheduling class. Enabling the /windfall allows the
    system to give a small amount of CPU time to a scheduling class
    when a CPU is idle and the scheduling class' allotted time has
    been depleted.

    To invoke the class scheduler, you use the SYSMAN interface.
    SYSMAN allows you to create, delete, modify, suspend, resume, and
    display scheduling classes. SYSMAN command: class_schedule shows
    the SYSMAN command, CLASS_SCHEDULE, and its sub-commands.

    Table 4-1 SYSMAN command: class_schedule

    Sub-
    command     Meaning

    ADD         Creates a new scheduling class
    DELETE      Deletes a scheduling class
    MODIFY      Modifies the characteristics of a scheduling class
    SHOW        Shows the characteristics of a scheduling class
    SUSPEND     Suspends temporarily a scheduling class
    RESUME      Resumes a scheduling class

    By implementing the class scheduler using the SYSMAN interface,
    you create a permanent database that allows OpenVMS to class
    schedule processes automatically after a system has been booted
    and rebooted. This database resides on the system disk in
    SYS$SYSTEM:VMS$CLASS_SCHEDULE.DATA. SYSMAN creates this file
    as an RMS indexed file when the first scheduling class is created
    by the SYSMAN command, CLASS_SCHEDULE ADD.

    In a cluster environment, SYSMAN creates this database file in
    the SYS$COMMON root of the [SYSEXE] directory. As a result, the
    database file is shared among all cluster members. By using
    SYSMAN's SET ENVIRONMENT command, you can define scheduling
    classes either on a cluster-wide or per-node basis.

    If desired, a system manager (or application manager) uses the
    permanent class scheduler to place a process into a scheduling
    class at process creation time. When a new process is created,
    Loginout determines whether this process belongs to a scheduling
    class. Given process information from the SYSUAF file, Loginout
    then class schedules the process if Loginout determines that the
    process belongs to a scheduling class.

    By using the SYSMAN utility to perform class scheduling
    operations instead of $SCHED system service, you gain the
    following benefits:

    o  You need not modify individual program images to control
       class scheduling. You can add, delete, and modify scheduling
       classifications from the SYSMAN utility.

    o  You can use SYSMAN to create a permanent class scheduling
       database file which allows processes to be class scheduled
       at process creation time and allows class definitions to be
       preserved in case of a system reboot.

    For more detailed information, refer to the following manuals:

       OpenVMS Programming Concepts Manual, Volume I
       OpenVMS DCL Dictionary: N-Z
       OpenVMS System Services Reference Manual: A-GETUAI