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Track and Block Counts
The number of tracks and physical blocks on the tape depend on the
following markers:
Physical beginning of tape (PBOT). PBOT is located at the point
on the tape where the translucent leader material is attached to
the media. This position is detected by an optical sensor in the
tape transport mechanism.
Logical beginning of tape (LBOT). When you issue a write
operation at the beginning of tape, the tape drive automatically
records LBOT at approximately 29 inches (74 cm) from PBOT. The
LBOT area includes tracks of LBOT information, which are used
to indicate the LBOT’s location, to calibrate the servo system and
to indicate whether the tape was written in uncompressed or
compressed format. The data contained in the LBOT blocks
cannot be altered or accessed by the user.
Logical end of tape (LEOT). LEOT is determined by the number
of recorded tracks that occur after LBOT. For this purpose,
lengths of erased segments are converted into an equivalent
number of tracks.
Physical end of tape (PEOT). PEOT is located at the point on the
tape where the translucent trailer material is attached to the
media. This position is detected by an optical sensor in the tape
transport mechanism.
The number of tracks between LBOT and LEOT depends on the type
and length of tape. Table 2-3 and Table 2-4 list the following
information for tapes written in various formats:
The number of tracks and 1,024-byte physical blocks between
LBOT and LEOT
The approximate number of tracks and 1,024-byte physical blocks
that occur between LEOT and PEOT
May 1994 EXB-8205 and EXB-8505 2-19
(Standard and XL)
2 Recording Format