2. PLANNING › 2.2 Supported MVS Data Structures › 2.2.7 DFHSM Backup Control Data Set (BCDS)

2.2.7 DFHSM Backup Control Data Set (BCDS)

VCC can optionally collect basic accounting and capacity
planning information about backup versions of data sets.
When DFHSM performs automatic backup of data sets, the BCDS
is updated with information about each backup copy or backup
version created on backup volumes managed by DFHSM.

The pyramid forms a useful analogy for considering the
potential amount of information processed by the VCC-DFHSM
interface for backup versions.  Consider this pattern of
usage for typical TSO users and the backup rules associated
with a "STANDARD" management class:

    o  25 percent of a given user's data sets are changed
       each day.

    o  An HSM rule states data sets are only to be backed up
       if they have been changed.

    o  A management class definition states that 5 backup
       versions are to be kept.

Thus, for an active data set that is changed every day, the
BCDS will contain information for 5 backup versions of this
data set in our hypothetical example above.

Expanding this scenario to an entire DASD complex, there
might be the following kind of relationship in terms of the
relative number of data sets:

                             /\
                            /  \
                           /    \
                          /      \
                         /        \
                        /  Primary \
                       /____________\
                      /              \
                     /                \
                    /                  \
                   /       Backup       \
                  /       Versions       \
                 /                        \
                /                          \
               /____________________________\


The VCC driver for DFHSM data collection anticipates a large
quantity of backup versions.  It is designed for optimum
execution time performance and optimum data compression of
the output file it creates.  Finally, you can collect data
about migrated data sets without collecting data about backup
versions (or vice versa).

Using VCC in conjunction with other CA MICS products, you can
establish different pricing for storage occupied for backup
versions.  Because the backup versions typically exist on
high-density tape cartridges, the relative charge for storage
occupancy (that is, amount of space times duration or
megabyte-days) is undoubtedly less for backup versions than
for primary DASD storage occupancy.  An example follows:

                             /\
                            /  \
                           /    \
                          /      \
                         /        \
                        /          \
                       /            \
                      /              \
                     /     $1.25      \
                    /       per        \
                   /    megabyte day    \
                  /______________________\
                 /                        \
                /          $0.05           \
               /            per             \
              /         megabyte day         \
             /________________________________\


Capacity planners can exploit this data by analyzing the
growth in backup versions over time, projecting the trend by
division or department using normal CA MICS techniques and
SAS procedures.