AT&T 3B2/300 Technical Reference Manual page 207

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23-MEGABYTE CARTRIDGE TAPE DRIVE (KS-23165,L1)
Cartridge Tape Use
One or more 23-Megabyte Cartridge Tape Drives can be added to a 3B2 computer. The drive can
be mounted in an AT&T Expansion Module cabinet or by itself in a Tape Module cabinet. One
23-megabyte cartridge tape drive is standard equipage with a 3B2/ 400 computer. Each 23-megabyte
cartridge tape drive connects to the host 3B2 computer via a CMl 95H Cartridge Tape Controller (CTC)
Card that is installed in a 3B2 computer feature card slot. For a 3B2/ 400 computer, the first cartridge
tape controller is equipped in slot 2. The primary use of a cartridge tape drive is as a streaming device
for backing up the data stored on the hard disk drives. While the 23-megabyte cartridge tape can be
configured as a file system, the intended use of a cartridge tape is as a streaming device. As a
streaming device, the tape provides a capacity of 45,539 blocks (512-byte blocks). The use of a
cartridge tape as a file system substantially degrades both system and tape performance.
Routine cleaning of the cartridge tape drive is required to maintain error-free operation. The CTC
card keeps track of the hours of operation. Software is provided to output an advisory message
warning of the need to clean the cartridge tape drive after 20 hours of operation. Depending on the
environment, more frequent cleaning may be necessary to maintain error-free operation and to promote
tape life. The recommended tape life in terms of pass count is 4000, when used as a streaming device.
If a tape is used as a file system, the pass count (tape life) should be reduced to 2000 or less.
The 23-megabyte cartridge tape can be formatted with a pass count threshold that is less than or
greater than the recommended value(s). Reformatting the cartridge tape does not reset the pass count
recorded on the tape. When the pass count recorded on a tape reaches the pass count threshold, an
advisory message is output to replace the tape.
EQUIPMENT DESCRIPTION 2-183