7. PARAMETERS › 7.1 TLM Component Parameters › 7.1.3 TLM Component Unit Level Parameters › 7.1.3.1 TLM Processing Options (TLMOPS) › 7.1.3.1.1 DURATIONS Statement

7.1.3.1.1 DURATIONS Statement

The DURATIONS statement is optional. It is used to override
the default values used by the TLM component to compute tape
data set space-time metrics (for example, megabyte-hours) for
both of the following scenarios:

o The first scan of a tape library by the Tape Management
  Catalog Collector (TMCC).

o A TMCC scan of a library where more than nn days have
  elapsed since the previous TMCC library scan.

Scenario 1 - First Scan of the TMCC
-----------------------------------

The TLM component provides a way to charge each tape data set
for tape media occupancy.  This is accomplished by computing
space-time data elements in the Tape Data Set (TMCTMD) file:

o TMDKBHR - Amount of Space-Time (KBytes-Hours)

o TMDMBHR - Amount of Space-Time (MByte-Hours)

During a TMCC scan, these metrics are computed by multiplying
the size of the data set by the lesser of these two:

o The number of hours since the last scan.

o The number of hours since the data set was created.

If this is the first TMCC scan of a tape library, potentially
enormous values could be generated for TMDKBHR and TMDMBHR
since there was no previous scan and many data sets could
have been created years earlier.  Therefore, during the first
scan, the TMCC uses the default value of 24 hours for all
tape data sets that were created more than 24 hours before
the current TMCC scan date and time.  Subsequent scans use
the difference between the current and previous scan dates
and times to compute space-time metrics.

Note: The default value is 24 hours because the expectation
is that you will normally schedule daily TMCC scans.

The DURATIONS statement allows you to override the 24 hour
default value used in the data set space-time computations
for the initial TMCC tape library scan.

Scenario 2 - Time Between TMCC Scans
------------------------------------

If the TLM component has been active in the past, but, for
some reason, has not been used for a long time and then is
reactivated, a situation similar to the first TMCC scan will
occur.  Because the component was used previously, the TMCC
scan job will be aware of the last scan date and time, which
could have been months or years earlier.

Using the difference between the current TMCC scan time and
the previous TMCC scan time would again result in excessively
large space-time metrics for older tape data sets.

By default, the TMC component allows a maximum value of seven
days between TMCC scans.  If more than seven days elapse
between TMCC scans, the component reverts back to the first
scan scenario and uses 24 hours in the computation of the
space-time metrics for older tape data sets.

The DURATIONS statement allows you to override the maximum
value allowed between TMCC scans to a value other than the
default value of seven days.

The DURATIONS statement has the following format:

DURATIONS sysid hh dd

where:

sysid  Is * or any valid SYSID value (up to four characters).
       Note that for the TLM component the SYSID data element
       contains the user-specified tape library name.  See
       Appendix C, TAPE MANAGEMENT CATALOG COLLECTOR (TMCC),
       for more information on SYSID specification in the
       setup of the TMCC collector.

hh     Is any integer number of hours from 1 to 24.

dd     Is any integer number of days from 2 to 99.

The default is:

DURATIONS * 24 7

where:

*   Means all SYSIDs (tape libraries)

24  Is the number of hours to use in the calculation of the
    space-time metrics for the first scan.

7   Is the maximum number of days allowed between scans
    before the calculation of the space-time metrics revert
    back to the initial hours (default 24) value.

If no DURATIONS statement is specified, the default values
are used.

Example:

DURATIONS * 24 30
DURATIONS TLM1 24 3

In this example, TMCC scan data from all tape libraries will
use 24 hours in the calculation of space-time metrics for the
first scan.  For subsequent scans, the space-time metrics
will use the lesser of the two durations (the time since the
last scan or the time since data set creation) unless the
last scan was more than 30 days ago.  If the time between
scans exceeds 30 days, the space-time metric calculations
will revert to 24 hours for data sets more than 24 hours old.

For tape library TLM1, the same 24 hours will be used to
compute the space-time metrics for the first scan.
Subsequent scans, however, must occur within 3 days for
calculation of the space-time metrics to use the previous
scan date and time.