5. OPERATION › 5.1 Operation Overview › 5.1.5 VCC Interface to DFHSM

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5.1.5 VCC Interface to DFHSM


If you code HSM=Y in VCCPARMS, VCCNTRL will ATTACH the module
VCCXHSM as a subtask to perform data collection about DFHSM-
owned data sets and volumes while VCCVTOC and VCCVSCAN
subtasks are asynchronously scanning VTOCs and catalogs.

VCCXHSM serves as a driver and control module for a module
called ARCUTIL.  IBM provides ARCUTIL in the DFHSM product
starting with DFHSM Version 2.5 and is available at Version
2.4 with proper enabling PTFs from IBM.  Chapter 17 of the
IBM publication "DFHSM Version 2 Release 5.0 Installation and
Customization Guide" (SH35-0084) thoroughly documents the
ARCUTIL feature.

ARCUTIL provides a standard method of collecting data from
the DFHSM Migration Control Data Set (MCDS) and the Backup
Control Data Set.  An application program provides a
parameter list and an OPENed DCB for the output file and
ARCUTIL reads the MCDS/BCDS and writes records to the DD
specified in the parameter list.  VCCXHSM is the driving
application program VCC uses to communicate with ARCUTIL.
DCOLLECT, available in DFP Version 3.2 and above, also uses
ARCUTIL to gather DFHSM data.

When IBM introduced ARCUTIL, they also added warnings that
application programs should not read the MCDS and/or BCDS
directly due to the probability of change in format with
future releases.

VCCXHSM uses ARCUTIL as described above and also intercepts
records formatted by ARCUTIL before they are written.  During
the intercept, they are reformatted as follows for the stated
reasons:

    o  Previous and current collection time stamps are added
       to the common segment of the record to allow CA MICS
       to compute DURATION, a critical element in an
       inventory-based measurement system.

    o  All variable length character strings are changed by
       stripping the field of blank padding characters and
       attaching the data elements as variable length
       strings.  The elements subject to this compaction
       process are:

       -  Data set name    (DSNAME)
       -  Management class (MGMTCLAS/STORMGTC)
       -  Storage class    (STORCLAS/STORSTGC)
       -  Data class       (DATACLAS/STORDATC)

       This compaction technique of VCCXHSM provides for
       substantial DASD space savings compared to the
       unmodified format of ARCUTIL-generated records (for
       example, those output by DCOLLECT).