2. USAGE GUIDELINES › 2.1 TLM Component Usage Guidelines › 2.1.2 TLM Tape Data Set Analysis

2.1.2 TLM Tape Data Set Analysis

The Tape Data Set (TMCTMD) file is used to analyze tape data
sets.  At the DETAIL timespan, the TMCTMD file contains
detailed information about each tape data set managed by the
tape management system.  At summarized timespans, the data
set name and volser are dropped, but the summarization keys
of the TMCTMD file provide enough granularity to support
sophisticated tape data set analysis, even at summarized
timespans.

Most data centers use a combination of traditional and
virtual tape.  Traditional tape satisfies requirements for a
variety of uses such as backup, offsite storage, isolation of
important files, and storage of very large data sets.
Virtual tape reduces the problems of inefficient tape media
use, contention for real tape drives, and excessive tape
volume mount time.

Tape management systems manage all tape data sets, but do not
identify whether a tape volume is virtual or real.  Tape
libraries support different tape cartridge types: high
capacity to optimize storage and lower capacity to optimize
speed of access.  In general, tape data sets with particular
characteristics are targeted for specific volser groups.

A best practice is to use the user-defined Volume Group
(VOLGROUP) summarization key element as a means to add
significant value to summarized TMCTMD file observations.

Section 7.1.3.2, TLM VOLGROUP Derivation Routine (VOLGPRTE),
explains how to use the VOLGROUP data element to group
together tape volsers with similar characteristics.  For
example, volsers used for virtual tape data sets could be
assigned one VOLGROUP element value (for example, VIRT TAPE),
while traditional tape volsers could be assigned another (for
example, REAL TAPE).

Using this simple example, at summarized timespans, all data
sets residing on real tape will be separated from those
residing on virtual tape.  Metrics such as average tape data
set size can be examined to see that expectations for virtual
tape versus traditional tape are being met.

Using the TMCTMD file, the analyst can probe numerous tape
data related characteristics such as these:

o Percent of data using compression
o Average size of data sets
o Duration between data set access
o Location
o Media type

Refer to section 5.1.2.1 for a comprehensive discussion of
the Tape Data Set (TMCTMD) file.