System Area; Data Area; Appending To Tape; Figure 27. Appending Rules - Seagate STD124000N Product Manual

Tape Formats
Product Manual

System Area

The System Area consists of the system preamble , the system log , the system
postamble, position tolerance band 2 and the vendor group preamble .

Data Area

The data area consists of the vendor group and one or multiple recorded data
groups . The vendor group is defined as basic group 0 (refer to the basic broup and
subgroup information above). Each recorded data group is equivalent to a single
basic group.
To ensure the highest possible data integrity, two methods are used.
First, the Scorpion 24 creates ECC3 (error-correction code 3) data, which provides
the capability to correct any two bad tracks in a recorded data group. The ECC3
data is derived from the 22 G1 subgroups of each basic group to form a 23
subgroup.
Second, to guard against normal expected tape defects, the Scorpion 24 uses read-
after-write capability to identify frames that have not been recorded correctly to tape
(read-after-write is described in detail in Chapter 8, "Theory of Operations", on page
71). When the drive identifies an incorrectly recorded frame, it is rewritten within a
maximum of 7 frames further down the tape. To skip elongated sections of defective
spots on tape, the rewrite operation may be repeated up to 255 times.

Appending to Tape

The DDS-3 format provides for seamless appends and nonseamless appends to
tape.
A
n
Frame Number:

Figure 27. Appending Rules

m Amble Frames
m ‡ 1
1 Frame
B
n + 2
C
n + 3 + m
Chapter 6
rd
G1
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