5190/5194 Modular Tape Subsystem Manual

Operating the Cartridge Tape Drive and ACL
5190/5194 Modular Tape Subsystem Manual—426878-002
4-49
Using MEDIACOM to Set the Systemwide
Compression Default Setting
Using MEDIACOM to Set the Systemwide Compression Default
Setting
MEDIACOM is the operator interface to the Distributed Systems Management/Tape
Catalog (DSM/TC). Using MEDIACOM commands, you can manage the tape catalog
(working with either labeled or unlabeled tapes).
Super-group users (user ID 255,n) can set the systemwide compression default setting
for your system by using the MEDIACOM ALTER MEDIADEFS command. (This
command affects only 5190 tape drives; compression is always on for 5194 tape
drives.)
The compression attribute of the ALTER MEDIADEFS command has two possible
settings: COMPRESSION IDRC and COMPRESSION OFF. The default setting is
COMPRESSION OFF. When you specify COMPRESSION IDRC, compression is set
on for 5190 tape drives.
To check and set the systemwide compression default setting:
1. Enter MEDIACOM at the TACL prompt:
20> MEDIACOM
MEDIACOM - T6028D30 (31OCT94)
Copyright Tandem Computers Incorporated 1993, 1994
MC>
2. Enter INFO MEDIADEFS at the MEDIACOM prompt (MC>) to display the current
systemwide setting for compression:
MC> INFO MEDIADEFS
Support Level NOCATALOG
Automatic OFF
Compression OFF
MC>
“Compression OFF” means that by default on this system, compression is not used
during a write to a scratch tape volume.
3. Use the ALTER MEDIADEFS command to set the systemwide compression
default setting on or off. For example:
a. To set compression on by default for this system:
MC> ALTER MEDIADEFS, COMPRESSION IDRC
b. To set compression off by default for this system:
MC> ALTER MEDIADEFS, COMPRESSION OFF
4. Enter EXIT to exit MEDIACOM and return to the TACL prompt:
MC> EXIT
21>