CP6100 I/O Process Programming Manual

File System Error Codes
If an LIU doesn't respond to a request, CP6100 tries up to three
times to establish contact through the CSM. In the meantime,
requests complete with error 124. If the LIU fails to respond
after three attempts at recovery, CP6100 declares the line down
and completes new requests with error 66. (Then an operator must
use CMI to download the line and return it to service.) If on
the other hand the LIU recovers, applications can resume their
use of the line.
If a status probe of the LIU reveals a malfunction, CP6100
attempts to recover according to the error. For instance, if
the probe reveals that power has returned, implying an earlier
failure, CP6100 downloads the LIU. If the SYSGEN AUTOLOAD
parameter is set, other problems revealed by the status probe
will also cause a download. Applications can resume their use of
the line, with the same considerations mentioned above.
POWER FAILURES
You find out about a power failure not when it occurs, but when
power is restored. Meanwhile, the device seems unresponsive:
• An LIU that has lost power fails to respond to a status probe
or to a frame sent by CP6100. Application requests complete
with error 124. If the LIU doesn't respond after several
attempts at recovery, CP6100 declares it down, and requests
complete with error 66. When power returns, the operator
must use CMI to start the line.
• A controller that has lost power may cause timeouts on the I/O
channel or a failure by an LIU to respond to a status probe.
This error may cause a path switch or a download of the LIU,
or both. If both controllers in a subsystem lose power,
requests complete every 30 seconds with error 231.
• If a BOB (the device that connects a controller to a group of
LIUs) loses power, there are several possible symptoms. LIUs
appear unresponsive, as in the case of an LIU power failure,
or a path switch occurs as in the case of a controller power
failure.
The rest of this section describes the file system errors and
gives some hints for recovery. Each book describing a protocol
also discusses error recovery; look for the heading "Recovering
from Errors" in Section 3.
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