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FAILSAFE tape format

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Tim Shoppa

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Jun 6, 2010, 1:07:13 PM6/6/10
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Usually I squeal with delight when someone turns up an old ROLLIN or
DSC format tape with goodies on it because for sure, those goodies are
35 years old or older. And... with some struggle against decaying
brain cells, I can usually remember what command line options will
help me read that tape!

I thought that an old FAILSAFE tape would be similar. Al found an old
DECUS collection tape (it's on bitsavers, http://bitsavers.org/bits/DEC/pdp10/magtape/decus
) with some read errors that purports to be FAILSAFE format. But my
struggles with FAILSA.EXE have yielded little.

Directory listings via /P just give me a bunch of tape errors. A read/
restore command /R gives the following:


.R FAILSA


REWINDS ARE NOT AUTOMATIC.
FAILSAFE VERSION 10100,47; FOR HELP, READ SYS:FAILSA.HLP, OR TYPE /H
*/W
*/R
12:42:25 06 JUN 110

5-SERIES FAILSAFE TAPE RECORDED BY VERSION
71 AT 01:59:30 30 MAR 72
"TAPE # 01


IF YOU WISH TO CONTINUE WITH THIS TAPE, TYPE "/C"
*/C


TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE ERROR READING HEADER; RECORD ACCEPTED

ILL FORMAT ON TAPE
SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE READ ERROR SEARCHING FOR EOF OR DIRECTORY RECORD

TAPE ERROR READING HEADER; RECORD ACCEPTED


Silly question after struggling with the 36-year-old FAILSA.EXE
executable: don't some versions of BACKUP know how to read FAILSA
tapes? How do I turn that on? Is the FAILSA format documented in some
Software Notebook?

Tim.

jmfbahciv

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Jun 7, 2010, 7:06:30 AM6/7/10
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Ok. IIRC, you will get these errors if the blocking factor is off or
the BPI is set incorrectly. Try reading with an 800 BPI.
Also try reading it with INTERCHANGE (now I'm not sure that was a
FAILSA switch). To check the readability of the tape itself, do a
DIRECT MTAn:/CHECKSUM

>
>
> Silly question after struggling with the 36-year-old FAILSA.EXE
> executable: don't some versions of BACKUP know how to read FAILSA
> tapes? How do I turn that on? Is the FAILSA format documented in some
> Software Notebook?
>

BACKUP can read FAILSA format but only in INTERCHANGE mode. You will
lose all directory information.

R BACKUP
/INTERCHANGE

If there are multiple savesets, you will need to do a RESTORE for
each save set. Also note that each save set could be at a different
BPI. The DIRECT command should give you a report of which BPI for
each saveset.

/BAH

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