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BACKUp and end-of-tape processing

Valentin Likoum
Frequent Advisor

BACKUp and end-of-tape processing

Hello all,

I wrote backup tape in the /NOREWIND mode, appending savesets one to one. Now I need to remove last saveset from the end of the tape. I tried it on the test tape:
$ back login.com;0 mkb400:test1/sav
$! point1
$ set mag /rewind mkb400:
$ dump/bl=cou=100 mkb400:
VOL1...
HDR1...
HDR2...
*** End of file ***
data blocks...
*** End of file ***
EOF1...
EOF2...
*** End of file ***
*** End of file ***
$! now append 2nd saveset
$ back login.com;0 mkb400:test2/sav/norew
$! now trying to put 2nd tapemark after
$! the 1st saveset to cut off 2nd saveset
$ set mag /rewind mkb400:
$ set mag /skip=file=3 mkb400:
$! now tape positioned at the HDR1 record of
$! the 2nd saveset
$ copy sys$input mkb400:
^Z
$! point2
$ set mag /rewind mkb400:
$ dump/bl=cou=100 mkb400:
... output is exactly the same as after the point1...

But backup on that crafted tape failed with
%BACKUP-F-LABELERR, error in tape label processing on MKB400:[000000]TEST2.;
-SYSTEM-W-ENDOFVOLUME, end of volume

But why? Content of the tape (till the double tapemarks) is exactly the same in the both cases (I checked it DIFFing the DUMP output). Tape drive is Tandberg DLT8000
Thank you.
15 REPLIES
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

Check help set mag /skip.
/skip=file:3 skips tape markers, not files.
Whatever that exactly means.

Wim
Wim
Bojan Nemec
Honored Contributor

Re: BACKUp and end-of-tape processing

Valentin,

Check also the SET MAG/END_OF_FILE which writes an end of file marker. Two end of file markers means end of tape.

Bojan
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

Also check help backup/rewind.

Per default, backup will write starting at eot.

Wim
Wim
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

You could try to do set mag/end before overwriting the last saveset.

Wim
Wim
Valentin Likoum
Frequent Advisor

Re: BACKUp and end-of-tape processing

to: Wim Van den Wyngaert
> Check help set mag /skip.
> /skip=file:3 skips tape markers, not files.

Yes, I know. I checked tape position before setting 2nd tapemark (DUMP/BL=COU=2 and rewind tape and skip files again)

> Also check help backup/rewind.
> Per default, backup will write starting at eot.

But I don't want to rewrite tape from the beginning (BACKUP/REWIND) but only the last saveset

> You could try to do set mag/end before
> overwriting the last saveset.

COPY SYS$INPUT MKB400: followed by ^Z and SET MAG /END (also suggested by Bojan Nemec) do exactly the same - they set tapemark in the current position and the result exactly the same: BACKUP-F-LABELERR,
-SYSTEM-W-ENDOFVOLUME.

Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

I tested it on 6.2 1h3 with set mag/end and it works fine. See enclosure.

Wim
Wim

Re: BACKUp and end-of-tape processing

I also tried couple of options:
When your tape is positioned somewhere, and you want one saveset back , you have to give:
$ set mag /skip=files=-4
If you want three savesets back, you have to specify:
$ set mag /skip=files=-12 !
Bit strange, but it works..

When you are positioned at the beginning:
$ set mag /skip=files=2
when you want to go to the next saveset
$ set mag /skip=files=4
when you want to skip 2 savesets

So when you go back double the numbers....
See the attachment

Also tried the same trich as Wim vd Wijgaert did, but got an error:
-SYSTEM-W-ENDOFVOLUME
See the attachment

I'm using a different version, 7.3-1

Jeroen Bleeker
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

In 7.2 HP added /fast to set mag.
Default depends on the tapedrive. But I guess my drive (TZ88) is doing /fast=never and your drive (?) is doing /fast=always.

May be the functionality is not exactly the same ? Try your test with /fast=never.

Wim
Wim

Re: BACKUp and end-of-tape processing

Wim: I use a TK89 drive. I tried it with the /fast option and your guess was good: it now works. Don't know if i'm going to use it but it's nice to know the futures..

Jeroen Bleeker

Re: BACKUp and end-of-tape processing

Hope to get my first points today..
Wim Van den Wyngaert
Honored Contributor
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

And skipping negative values too. Values under 3 are slow. Above are fast.

Wim
Wim
Wim Van den Wyngaert
Honored Contributor

Re: BACKUp and end-of-tape processing

And give me a couple of zeroes for underestimating you. I learned from this thread.

Wim
Wim
Valentin Likoum
Frequent Advisor

Re: BACKUp and end-of-tape processing

Hmm.. Tried to play with /fast=always and /fast=never. /fast=never gives desired result on the test tape but doesn't work on the target tape. Get bored after all and took another empty tape :)