Quantum DLTtape DLT 4000, Product Manual

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Quantum DLT 4000 Tape System B-1
Appendix B
EEPROM-RESIDENT BUGCHECK AND EVENT LOGS
This appendix provides an explanation of the event logs (information packets) stored in semi-
permanent, non-volatile memory of the tape drive. These packets can be retrieved via the SCSI LOG
SENSE command with Page Code 07h.
B.1 EEPROM PACKETS (LAST N EVENTS)
The tape drive keeps certain event logs in semi-permanent, non-volatile memory
(EEPROM, in this case) located on the tape drive’s controller PCB. There is
storage enough within EEPROM for a total of 14 of these logs, or packets, each
packet consisting of 98 bytes (96 data bytes plus two control bytes) of
information. Packets may be written for different reasons and several packet
types exist.
The information in the event logs does not indicate that a tape drive or tape
medium has failed but is useful in isolating problems that may be occurring.
The logs are maintained in a circular buffer: a new entry overwrites the oldest
existing entry. At any point in time, the most recent 14 logs are kept.
The EEPROM information packets can be retrieved via the SCSI-2’s LOG
SENSE command with Page Code 07 (Last n Error Events Page).
The packet type field defines the content as well as the format of the data
portion of the packet. These packet types are detailed in this Appendix. Note
that the byte offsets in the structure layout diagrams are reference relative to the
beginning of the 98-byte EEPROM log envelope.
B.2 BUGCHECK PACKETS
Bugchecks are the result of some software-detected errors. For example, a
hardware failure or an internal system consistency failure may cause a bugcheck.
These events cause bugcheck packets to be written to EEPROM.