5. OPERATION › 5.1 Operation Overview › 5.1.1 VCCNTRL - Initialization, Control and Reporting

5.1.1 VCCNTRL - Initialization, Control and Reporting

The VCCNTRL module is responsible for VCC initialization,
subtask ATTACH control, and VCC reporting after all
processing has been completed.  VCCNTRL performs the
following functions:

    o  Acquires the VCC Common Work Area (CNTWA).  This work
       area is addressable by all of the VCC modules and
       contains DCBs, parameter data set specifications,
       queue anchors, and general storage areas.

    o  OPENs the VCCVTMSG, VCCVSMSG, VCCSTATS, VCCDATA (if
       VCC recording to a data set has been requested), and
       VCCSNAP data sets.  RDJFCBs are issued to make sure
       that the DD cards are present.  In the case of the
       VCCDATA data set, the disposition is forced to be
       DISP=OLD via OPEN TYPE=J.

    o  LOADs all of the VCC modules that will be called as
       subroutines by the various VCC tasks.

    o  Calls VCCPARSE to read in and parse the parameter data
       set VCCPARMS (if specified).

    o  Scans the MVS DASD UCBs and builds a volume table that
       contains entries for every DASD volume on the system.

    o  Validates and OPENs the VCCNTROL data set.  If this
       data set has not been initialized (is empty), then the
       previous VCC process timestamp is calculated to be 24
       hours prior to the current VCC run timestamp.
       Otherwise, the VCCNTROL data set is read in, the
       previous VCC run timestamp is set to be equal to the
       last VCC run timestamp, the volume table is updated
       with the previous process timestamp of each volume (as
       indicated in the VCCNTROL data set), and the
       configuration SMF record is written.  This SMF record
       is equivalent in content to the volume table.

    o  Builds a table called the VTOC Scan Control Table
       (VSCT).  This table consists of up to 16 primary
       physical channel headers.  Each PCHAN header points to
       a list of DASD string elements that in turn contains
       unit elements for each device to be scanned.  The VSCT
       is created for two reasons:

         - To provide a means by which VTOC and catalog I/O
           generated by VCC can be spread across the DASD
           configuration.  To do this, VCC must first know
           what the configuration looks like.

         - To provide areas in which to maintain statistics
           on each device scanned.

       The INCLUDEVOL/EXCLUDEVOL, INCLUDEDEV/EXCLUDEDEV, and
       INCLUDEDV4/EXCLUDEDV4 parameters control the devices
       in this table.  If you wish to include or exclude DASD
       devices by device address, use INCLUDEDEV/EXCLUDEDEV
       if your installation uses 3-digit UCB device
       addresses, and INCLUDEDV4/EXCLUDEDV4 if you use
       4-digit UCB device addresses. Only one of the
       following parameters may be specified for a VCC scan:
       INCLUDEDEV, EXCLUDEDEV, INCLUDEDV4, or EXCLUDEDV4.

    o  ATTACHes the VCCVCNTL (VSAM catalog scan control)
       subtask.  VCCVCNTL will in turn ATTACH the number of
       VSAM/ICF/VVDS catalog scan subtasks specified by the
       VSAMSUBT parameter.

    o  ATTACHes the number of VCCVTOC (VTOC scan) subtasks
       that were specified by the VTOCSUBT parameter.

    o  Calls VCCWRITR at entry point VCCWRIT2 to write
       records queued in the writer buffers to the proper
       data sets.  After all records have been written and
       all subtasks have terminated, VCCWRIT2 returns to
       VCCNTRL.

    o  VCCNTRL updates the VCCNTROL data set with current VCC
       run information and writes the VCC Run Status Report.