BACKUp and end-of-tape processing

[Valentin Likoum]

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.

[Wim Van den Wyngaert]

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

Wim

[Bojan Nemec]

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]

Also check help backup/rewind.

Per default, backup will write starting at eot.

Wim

[Wim Van den Wyngaert]

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

Wim

[Wim Van den Wyngaert]

Also check this
http://groups.google.com/groups?hl=nl&lr=&threadm=9306021421.AA12830%40uu3.psi.com&rnum=5&prev=/groups%3Fq%3Dmagtape%2520site%253Ahp.com%2520skip%2520%26num%3D100%26hl%3Dnl%26lr%3D%26sa%3DN%26tab%3Dwg

Wim

[Valentin Likoum]

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]

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

Wim

[Jeroen Bleeker_2]

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]

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