Digital Equipment RW504-ZA, Service Manual

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6.6.5 Hardware Error Codes
If an error is unrecoverable (i.e., something is broken or jammed to a point that
manual intervention is required), the autochanger takes an additional step in an
attempt to identify the Field Replaceable Unit (FRU) that is causing the failure.
A routine is called automatically that performs a process of elimination for
various FRUs. This routine attempts to isolate the error to three (or less) FRUs.
If no error can be found (or if recovery was made from the error), the unit returns
a ‘‘no error’’ status. If an error is found, a hardware error code and a move
error code is returned when the command completes. Up to three FRU numbers
are returned. The FRUs, and a time stamp, are listed in decreasing order of
probability.
Hardware Error Codes are listed in Section 4.7
6.6.6 Real Time Event Logging
Logs
The optical disk library provides information logs about its operation and error
history. These logs provide predictive information that can lead to early detection
of autochanger problems.
All logs are maintained within the nonvolatile RAM and are accessible through
the control panel and by the SCSI Log Sense command over the SCSI interface.
The main functions provided with operational logs are described below.
Error Log
The autochanger maintains a history of past diagnostic test errors that have
occurred within the autochanger, along with a time stamp of when they occurred.
The error message maintained for each error indicates the failure and the possible
FRUs that may have caused the failure.
Move Success Log
A cumulative number of move recoveries and a total move count are maintained.
This gives service a view of the history of the autochanger soft error rate. The
last ten hard errors are marked in this log by indicating how many good moves
occurred since the last hard error.
Force Log
Each cartridge move is actually a sequence of many small moves, known as
micro-moves. This log is a record of the maximum force measure during every
micro-move situation.
Recovery Log
This is a record of recoverable (soft) errors, and related information on error
recovery methods used and their success or failure.
6–26 Theory of Operation