Tandberg Data
Data Reliability
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Tandberg SLR Reference Manual
5-3
5.3. Write Mode
Data is immediately verified by a read-while-write check. The read channel has stricter
acceptance levels during this operation to detect marginal recordings. The Drive will verify
that each block has got the correct Block Address, Block Marker and CRC character. The
complete block is checked by using the CRC generator. All failing blocks will immediately be
rewritten.
Checking List
The complete list of data checking is:
•
A CRC check is performed on each data block.
•
All read data is checked against the coding table for GCR or
RLL encoding - any deviation from this table is marked as
an error
•
For every block the Drive verifies (by reading) that the
Block Marker is correctly recorded
•
If a Write operation is not successfully completed, the tape
will be repositioned and Write Retry will be executed
5.4. Read Mode
Retry Procedure
If a data frame has more errors than can be handled by the ECC system, the Drive will enter
a Read Retry algorithm. This algorithm includes the following operation:
•
Off-centering the head position
•
Modifying the read equalizer
•
Modifying the Read Threshold
5.5. Cartridge Conditioning
Conditioning Rules
The achieveable data reliability is depending on the tape and cartridge quality. In order to
obtain the lowest error rate possible on a given cartridge, the cartridge should be conditioned
according to the following rules before being used:
‘•
Before use the cartridge should be conditioned by expo-
sure to the actual operating environments for at least 8
hours. (Refer to Section 3.3.1 for the operating environ-
ment specifications).
•
In Read Mode: If an “Unrecoverable Read Error” occurs,
the magnetic head should be cleaned, and the read opera-
tion started once more and fail on the same block before
this error is classified as permanently unrecoverable.
•
Before using a new cartridge for the first time a complete
retension operation is recommended (tape run from BOT
to EOT and back - duration up to 7 min depending on tape
length).