IBM 7074 General Information Manual page 23

Action 3
l. Execute part 1 of action 1 as many as four times.
Exception: In the case of a write check, the original
sequence should be repeated, not part 1 of action 1:
prepare to verify, subsequent write, prepare to verify,
and write check.
2. After a fifth error indication, print message 1.
Action 4
l. Seek to any track address ( 0000-9999). This
moves the access mechanism from the customer engi·
neering track to cylinder zero.
2. Seek to the desired track. Prepare to verify and
read or write.
3. If the error condition persists, print message l.
Message 1 Format
Message 1 identifies an uncorrectable error. Further
procedure is determined by the application.
Minimum: 1-4, inclusive
Recommended, if core storage permits: 1-8 inclusive
Maximum: 1-10
l. xxxx: a message code used when the message is
associated with a halt or waiting loop.
2. Type of Error: read, write, write check, or control.
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3. Unit Involved: access number, module number,
track number.
4. File Control Status Word: bytes 0-4 inclusive; an
examination of byte 0 will reveal any multiple error
conditions.
5. Channel designation and final status or control
word for the channel at the time of the error.
6. File Control Status Word: bytes 5-9 inclusive.
7. Nature of Data: packed or unpacked.
8. Preceding control orders.
9. Previous Unit Involved: access number, module
number, track number;
FROM
address, the previous ad-
dress sought on the module in error.
10. Current Unit Involved: access number, module
number, track number;
TO
address, the address to
which the access mechanism was going, or had
reached, at error time.
Statistical Print-out
At the end of a program segment or run, or at a con-
venient time interval, a Message 2 should be printed.
Message 2 Format
l. Access number, module number.
2. Number of entries into error routine.
3. Number of Message 1's printed (uncorrectable
errors) .