2. USAGE GUIDELINES › 2.3 Miscellaneous Usage Notes for All Files › 2.3.1 The Inventory Nature of the Data

2.3.1 The Inventory Nature of the Data

As you begin using the data in the various VCA and HSM
database files, it is useful to understand the method by
which the information is collected.  The CA MICS Space
Collector (VCC) literally takes an "inventory" of the DASD
subsystem at a given point in time.  By scanning the various
control resources (VTOCs, catalogs, DFHSM control data sets)
in this highly-efficient "snapshot" approach, we are able to
produce a reasonably accurate inventory of data about your
data.

VCC has a wide variety of recording options.  When we refer
to the "production" use of VCC and the "production" use of
the CA MICS VCA and HSM information areas, we make the
assumption that the collector has captured data about the
entire DASD configuration.  While it is possible and
desirable to subset the DASD "farm" for special studies
needed by storage administrators, these special-purpose views
of the DASD farm are by their very nature, incomplete.  Just
as you would not call the inventory of an auto-parts store
complete if you only counted the sections that containing
motor oil, coolant, and floor mats, you would not deem a DASD
inventory complete if you only measured a few volume pools or
omitted HSM backups.

Thus, it is important to be always aware of the underlying
VCC collection job stream and the options used by VCC at
collection time.  Try to relate one set of VCC recording
options, VCC JCL (including the data sets output by VCC), and
VCC scheduling frequencies with a CA MICS database unit. For
example, Chapter 9 discusses some exception reports logged
to the MICSLOG SYSOUT data set during DAILY processing.
These clusters of messages are closely connected to the data
collection function and frequently, the resolution of an
exception is tied back to the data collection job output.
Chapter 3 of the CA MICS Space Collector Guide describes the
VCC output in great detail.

Another example of the inventory nature of the data
collection relates to DFHSM. VCC as a "production inventory"
should be run immediately before DFHSM "daily space
management" is initiated.  Because DFHSM sweeps the volumes
under its management and migrates or deletes data sets
according to its wide-range of rules, the inventory VCC takes
will reveal day-to-day trends more clearly if it is
consistently positioned relative to these DFHSM actions.
Alternatively, you could schedule production VCC inventories
to run immediately after the completion of DFHSM daily
processing. You should avoid inconsistency.

In contrast, you can perform on-demand data collections with
processing into special or test CA MICS unit databases at
any time of day or at any frequency.  Take care to avoid
destruction of important VCC data sets used by the
"production VCC".