TLM DURATIONS Statement (Optional)

The DURATIONS statement 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:
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  • The first scan of a tape library by the Tape Management Catalog Collector (TMCC).
  • 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:
TMDKBHR
Amount of Space-Time (KBytes-Hours)
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:
  • The number of hours since the last scan.
  • 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 because 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 typically 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
sysid
This parameter is * or any valid SYSID value
Limits:
4 characters
Note:
The TLM component the SYSID data element contains the user-specified tape library name. For more information about SYSID specification in the setup of the TMCC collector, see Tape Management Catalog Collector (TMCC).
hh
This parameter is any integer number of hours from 1 to 24.
dd
This parameter is any integer number of days from 2 to 99.
The default is:
DURATIONS * 24 7
*
Means all SYSIDs (tape libraries)
24
The number of hours to use in the calculation of the space-time metrics for the first scan.
7
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.