Use of the IDRC Report

The IDRC Report shows the potential effects of using IDRC compaction, 3490E enhanced recording format, and the Enhanced Capacity Cartridge System Tape with large data sets. If you use IDRC compaction on a data set that resides on four volumes, you can make it fit on one volume.

To understand the numbers generated for this report, it is important to note the following:

The IDRC Report shows the data set level detail for the large category savings reported in the Estimate Report. To determine the summary of total savings, request only the Estimate Report.
This report does not process from the volume perspective. For example, it does not show which tapes are suitable for IDRC/3490E.
The IDRC Report only includes data sets larger than the value specified with the LARGE keyword. It shows the volumes and mounts associated with each of these data sets. In the tape mount management methodology, these data sets are large enough to make good use of a cartridge and would go directly to tape.
GFTAVMA assumes that DFSMS intercepts data sets smaller than the LARGE value (default 600MB) and re-routes them to the tape mount management DASD buffer storage group. The effects of IDRC, 3490E, and double capacity cartridges are modelled for these smaller data sets when they are eligible to be migrated to tape with DFSMShsm, based on the values specified or defaulted for the IDRC, TAPEDEV and TAPELEN keywords.
Because GFTAVMA analyzes tape processing over time, it is possible to have data sets included in the sample that no longer exist because the volumes associated with these data sets have been reused for other data. These data sets are still accounted for in the IDRC Report because, if you had used IDRC compaction at the time the data sets were written, you could have saved volumes and mounts.
If the savings from using IDRC and 3490E are less than anticipated, it might be because the majority of your tape data sets are single volume and do not show volume or mount savings that result from using these techniques directly. You can enhance the benefits dramatically by using the principles of tape mount management to ensure that all cartridges are automatically filled with data and thus can benefit from compaction and 36-track recording.