ClearPath OS 2200 Series Release 13.2 Software Planning and ...

Tape and DVD
4.6.3. 36-Track Tape Subsystems
The 36-track tape technology provides for double density and longer tape lengths. The
Exec provides unique equipment mnemonics for configuring 36-track tape subsystems
and unique file/tape assignment mnemonics for assigning tape files to this type of
medium.
This subsection provides the following information:
• General considerations for 36-track tape subsystems
• Specific considerations by subsystem
− CTS5136
− OST5136
− CTS5236
− OST4890
• General tape mnemonic enhancements
• Coexistence with other cartridge tape subsystems
• Fast tape access
General Considerations for 36-Track Tape Subsystems
Consider the following when migrating to 36-track capability:
• The 36-track tape drives use a new tape format to record more data than 18-track
tapes. Eighteen tracks are written in one direction, and then another 18 tracks are
written from the end to the beginning of the tape. Therefore, twice as much data can
be recorded on 540-foot cartridge tapes.
• Extended cartridge tapes (called E-tapes) are available for use in 36-track drives.
E-tapes are 1,100 feet long—about two times longer than current cartridge tapes.
Therefore, E-tapes can hold up to four times as much data as current 18-track tapes.
Note: E-tapes should not be inserted in 18-track drives. Damage to the device or
tape might occur.
• Rewind time is virtually eliminated when a full tape is written in 36-track format
because the tape has been written from the beginning to the end and back to the
beginning.
• The Exec returns an I/O error status 6 when a write of an I/O block greater than 256K
bytes is attempted to a 36-track device.
• All 36-track tapes are interchangeable between 36-track tape devices.
• For most 36-track tape subsystems, read backwards I/O functions are not supported
and are terminated with an I/O error status 024. However, this is not the case for
CTS5136 tape subsystems. For these subsystems, the Exec returns an I/O error
status 6 when a read backward of a partial or nonintegral EDRC block is attempted.
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