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Checking the Reliability of the Tape Data
After the Streaming Tape Drive Utility completes a list or restore operation, the
message “Reliability: Tape drive recovered from xxx soft errors” appears, with xxx
representing the number of 512-byte blocks that could not be read successfully on
the first attempt. However, the tape drive was able to recover the data successfully
using either a read retry or ECC. The hardware specifications allow up to one soft
error for every 102 KB of data, but testing has shown that a typical list or restore
operation of 4 GB of data would only have one soft error for every 1 MB to 14 MB
of data. For example, if a tape is full (it has 4 GB of data), it may have over 200
soft errors.
When the Streaming Tape Drive Utility is exited, a W660 B4/S055/E010 message is
logged to record the number of soft errors encountered while the utility was
running. If you format the W660 message using the Long Format Mode of the Scan
System Log Data Utility in the Controller Events bucket, the following line
appears:
DATA ERRORS: XXX UNDERRUNS: XXX PARITY ERRORS: XXX
The DATA ERRORS field shows the number of soft errors that were recovered
using a read retry. The UNDERRUNS field is not used for the TR-4 Tape Drive and
always shows 0. The PARITY ERRORS field indicates the number of soft errors
that were recovered using ECC.
Listing a Tape
The directory information for each file on the tape is located immediately before
the file data for each file. It does not have a separate directory. Therefore, listing
the data on the tape requires reading all of the data on the tape. A full tape of
4 GB of data would require about 2.5 hours to list the tape at the rate of 30 MB
per minute. It is recommended to list the tape after each backup. The list can be
used to verify that the data can be successfully read if required.
Erasing a Tape
Erasing a tape takes approximately three minutes. The process writes an
End-of-Data marker at the beginning of the tape, winds the tape to the end, and
then rewinds back to the beginning in order to retension the tape.
Messages
This section describes the messages specific to the TR-4 Tape Drive.
W679 W679 STREAMING TAPE DRIVE
ERROR B4/S056/Exxx
Severity: 3
Explanation: The attempted streaming tape drive
operation cannot be performed.
The event (Exxx) in the message indicates the
following:
E019 – Peripheral device write fault. This normally
indicates a hardware problem with the tape
cartridge.
E020 – No write current.
E021 – Excessive write errors.
E022 – Logical unit not ready, cause not reportable.
E023 – Logical unit is in process of becoming ready.
E024 – Logical unit not ready, initializing command
required.
14 TR-4 Tape Drive User’s Guide