Tape Layouts In The Dds-3 Standard; Layout Of A Single Data Space Tape (Single Partition); Figure 25. Timing Tracking - Seagate STD124000N Product Manual

Tape Formats
Product Manual
Subcode
Active track
Case 1: The head is off track because the tape is moving too fast.
Too much time elapses before the heads read the subcode.
To bring the heads on track, the drive automatically slows the tape.
Case 2: The head is on track, and no corrective action is necessary.
Case 3: The head is off track because the tape speed is too slow.
Too little time elapses before the heads read the subcode.
To bring the heads on track, the drive automatically increases
the tape speed.

Figure 25. Timing Tracking

The PG position is a known constant which is based on the fixed mechanical
positions of the PG sensors and the heads within the cylinder. These relative
positions do not change and can be used as a solid baseline for the timing
calculations. Also, because there are separate PG pulses associated with each
recording head (A and B), accurate timing tracking can be achieved even under
adverse conditions.
To ensure optimum accuracy, a calibration is performed whenever a recorded tape
is inserted into the Scorpion 24. This calibration determines the target time against
which all succeeding measurements are compared.

Tape Layouts in the DDS-3 Standard

The DDS-3 standard provides for two types of overall tape layouts, single data
space tapes and partitioned tapes. The following two sections describe the specific
layouts for each.

Layout of a Single Data Space Tape (Single Partition)

The DDS-3 recording format supports both single data space tape (nonpartitioned)
and partitioned tape . You can record a tape as either a single data space tape or as
a partitioned tape.
The tape layout for a single data space tape contains six areas: the device area,
the reference area, the system area, the data area, the EOD area and the post-EOD
area.
Read Head
Chapter 6
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