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9. Set the correct mode (if seven-track), and send the track-in-error
information (sense byte 2) to the tape control with a
TIE
command.
10. Issue a read command in the opposite direction (Read Opposite ccw) with
the suppress data transfer bit on.
11. Repeat steps 7 through 10 until the block is read successfully or at least 41
attempts have been made. If the block is read successfully, determine the
number of attempts left and go to step 12. If, after 41 attempts, the Read
Opposite ccw is still unsuccessful, go to step 19.
Note: After every fourth try, perform a tape cleaner sequence.
12.
If
the actual block count is greater than the failing original Read ccw count,
go to step 19.
If the actual block count is equal to or less than the failing Read ccw count,
compute the correct data address and count for the Read Opposite ccw.
Proceed to step 13.
13. Determine if the block should be classified as a noise block. See Action V,
step 1.
14. Set the correct mode (if seven-track), and reposition tape.
15. Set the correct mode (if seven-track), and send the track-in-error information
(sense byte 2) to the tape control with a
TIE
command (if nine-track).
16. Issue the Read Opposite ccw with the computed address, the count, and the
suppress data transfer bit off.
1 7. Repeat steps 13 through 16 until the block is read successfully or the
remainder of the 41 attempts have been performed. If the block is read
successfully, go to step 18.
If
after attempting 41 tries, the Read Opposite
ccw is still unsuccessful, go to step 19.
Note: After every fourth try, perform a tape cleaner sequence.
18. Set the correct mode (if seven-track). Space over the error block, post
completion without error condition, and continue with normal processing.
19. Set the correct mode (if seven-track), and reissue the read or read backward
command.
If
the error persists, provide an operator message, post completion with error
condition, and exit to the operating system. See "Terminal Action
Ia"
and
"Supplementary Information."
Action VI (Data Check On Write and Write Tape Mark)
Reposition the tape, issue an Erase Gap
(ERG),
issue a Mode Set (if
seven-track), and reissue the command. For a Write, repeat this procedure until
successful or until 15 attempts have been made.
If
the error persists through 14
retries, go to Step 1.
For a Write Tape Mark, repeat this procedure until successful or until 16
attempts have been made.
If
the error persists through 16 tries, go to Step 2.
Step 1:
Change the failing Write ccw to a Loop-Write-To-Read ccw to obtain data for
error recording.
·
The Loop-Write-To-Read ccw mv"t not be command chained or data chained
from or to any of the ccws in the original failing ccw chain. (Such a chain
could cause tape movement and destruction of previously written tape records.)
54
3803-2/3420 Subsystem Description
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