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Managing Tape Drives
L700 (CTL700) Installation and User’s Guide—527338-004
9-14
Controlling Data Compression
3. Set compression on or off. For example:
a. To set compression on by default:
MC> ALTER MEDIADEFS, COMPRESSION IDRC
b. To set compression off by default:
MC> ALTER MEDIADEFS, COMPRESSION OFF
4. Enter EXIT to exit MEDIACOM and return to the TACL prompt:
MC> EXIT
->
For more information about MEDIACOM and the ALTER MEDIADEFS
command, see the DSM/Tape Catalog Operator Interface (MEDIACOM) Manual.
Using DEFINE to Override the System Compression Default
The systemwide compression default specification set by the MEDIACOM
ALTER MEDIADEFS command applies to the labeled and unlabeled tapes.
After the default specification is set, the drive always writes using the default
setting. To override the default specification for a specific job, use a CLASS
TAPECATALOG DEFINE.
A CLASS TAPECATALOG DEFINE is a named set of attributes and values that
specify information about a tape file. If labeled tape is used, a CLASS
TAPECATALOG DEFINE must be created for each tape file to be accessed
before the tape can be used.
Using a CLASS TAPECATALOG DEFINE
There are two types of tape DEFINEs:
•
CLASS TAPE DEFINEs
•
CLASS TAPECATALOG DEFINEs
If the DSM/Tape Catalog software system is being used, a CLASS
TAPECATALOG DEFINE must be used. A CLASS TAPECATALOG DEFINE is
similar to a CLASS TAPE DEFINE, but the CLASS TAPECATALOG DEFINE
has two additional attributes:
CATALOG { ON | OFF }
Requests the services of the DSM/Tape Catalog (which might not be
installed on the system). Specify OFF to use the CLASS TAPECATALOG
DEFINE template without using DSM/Tape Catalog. Specify ON to use
the DSM/Tape Catalog.
Attribute Options
CATALOG ON or OFF
COMPRESSION IDRC or OFF