Chapter 4. Controls, Indicators, and Operation of 10/20-GB DLT Cartridge Tape Drive
Order Number: EK–SM1TB–UG. E01
4–15
4.7.1.1 Selection of Compression Mode
Depending on the type of data involved, the compression capability o the 10/20-GB DLT
Tape Drive can store up to double the amount of data on a tape. This compression capability
is another density selection. When the tape drive is operating in regular TZ87 mode (only the
yellow TZ87 indicator is lit), the tape drive can store up to 10 GB on a regular CompacTape
III DLT data cartridge and can transfer data (read or write) at a rate of up to 1.25 MB/s.
When the tape drive is operating in compressed TZ87 mode (both the yellow TZ87 indicator
and the adjacent C
OMPRESS
indicator are lit), the tape drive can store up to 20 GB on the
same cartridge and can transfer data (read or write) at a rate of up to 2.5 MB/s (assuming a
2:1 compression ratio).
4.7.1.2 Density Select Example
Suppose, for example, that you have installed a tape with a prerecorded TK85 density, and
you use the density-selection push-button to select the TZ87 density. You should observe the
following:
•
The D
ENSITY
O
VERRIDE
indicator is lit, indicating that a density selection has been
made from the front panel.
•
The TK85 indicator initially lights and remains lit, indicating the initial density selec-
tion of the current tape.
•
After you toggle the density-select switch to make the TZ87 indicator blink, the drive
keeps that indicator blinking, indicating that a density change is pending, while the
TK85 density indicator remains steadily lit during the writing process.
After a write from BOT occurs, you should observe the following:
•
The TZ87 indicator becomes steadily lit.
•
The TK85 indicator goes out.
•
The D
ENSITY
O
VERRIDE
indicator remains lit.
If you now activate the density-select mode again (by momentarily pressing the D
ENSITY
S
ELECT
push-button) and then press that push-button one more time, the tape drive goes into
its compression mode: the TZ87 indicator remains lit, but the adjacent C
OMPRESS
indicator
also lights. Compression mode, which is available only for the TZ87 density, lets the tape
drive read or write at twice the transfer rate and data capacity of the uncompressed mode
(again, assuming a 2:1 compression ratio on the data).
4.7.2 Density Selection Rules
Density selection occurs in accordance with the following rules (See also Table 4–10):
READ or WRITE APPEND Density Selection
The indicator on the left side of the front panel of the drive will designate the density of the
tape currently mounted in the drive.
