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Error Priority
Error priority is as follows (highest priority is 1):
1.
Channel control check.
2. Interface control check.
3. Storage-protect or program check.
4. Chain check.
5. Incorrect length indication (IL!).
6. Data check.
If
any of these errors occur simultaneously, the
higher priority error will reset the lower priority
error. There is one exception to this rule. On a
write operation when the channel prefetches either
an invalid CCW on data chaining or data with an in-
valid data address (storage-protect or program
check), an incorrect length indication will reset the
storage-protect or program check.
Data-check error is blocked from setting if a
higher priority error occurs at the same time but
is not reset if
it
is already on.
Diagnostic Techniques
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