5190/5194 Modular Tape Subsystem Manual

Operating the Cartridge Tape Drive and ACL
5190/5194 Modular Tape Subsystem Manual—426878-002
4-45
Using TMDS to Check the Compression Mode
Status (NonStop Himalaya K-Series Servers)
The COMP LED becomes unlit when the drive reads or writes uncompressed data or
tape marks (also referred to as file marks). The LED remains unlit during loading,
unloading, and rewinding.
During normal operation, prefetching of data causes the COMP LED to flash on and off
more frequently when the drive reads data than when it writes data.
Using TMDS to Check the Compression Mode Status (NonStop
Himalaya K-Series Servers)
To determine the compression mode of the last write operation, use the TMDS
STATUS command. To use this command for a tape drive named $TAPE1, enter:
>TMDS TAPE
TAPE>STATUS $TAPE1
The information displayed for $TAPE1 includes the compression mode of the drive.
For an example of the display, see The STATUS Command on page 5-5.
The TMDS STATUS command does not show the current compression mode of the
drive; rather, it shows the compression mode of the last write operation. The display
reflects changes in the systemwide compression default setting only after a write
operation. To see the current compression mode with TMDS, you can use the TMDS
MONITOR command. For more information, see the TAPE subsystem information in
the TMDS Reference Manual.
You can determine the system default specification for compression by using the
MEDIACOM INFO MEDIADEFS command as described in Steps 1 and 2 of Using
MEDIACOM to Set the Systemwide Compression Default Setting on page 4-49.
Methods for Controlling Compression
Table 4-10 lists the ways to control compression for the 5190 drive.
Table 4-10. Methods for Controlling Compression on a 5190 Tape
Drive (page 1 of 2)
Method Description Page
PERIPHERALS
paragraph
modifier
(K-series only) This is a convenient way of permanently setting
the compression mode for a 5190 tape drive if you are not using
MEDIACOM. (The MEDIACOM systemwide default setting
overrides the PERIPHERALS paragraph setting.)
4-46
COUP (K-series only) If there is no systemwide default setting, you can
use the COUP compression device attribute to enable or
disable compression for a 5190 tape drive you are configuring.
(The MEDIACOM systemwide default setting overrides the
COUP setting.)
4-47
MEDIACOM The MEDIACOM ALTER MEDIADEFS command sets a
systemwide compression default setting.
4-49