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Multiple savesets on a dlt tape

 
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MarkOfAus
Valued Contributor

Multiple savesets on a dlt tape

Hi all,
It may be because I have not done this for ages, but anyway:

Backups for a system are done to one single tape, such as (apologies if the formatting is bad):
$ backup /media=compact /block=32256 /record /fast -
/ignore=(inter,label) 'exclude_list' -
/log -
'device'[*...] tape:'label'/save
$

There can be up to 4 savesets on a single tape, or they may indeed span onto another tape. In this case, there are 3 savesets on the tape.


So, if I mount the tape, eg mount mkd400 may01, for example, I can see the savesets and even copy them from the tape to a disk, but I can't use backup to extract them straight off the tape.

So when I do the mount/for/nounlo mkd400, then a backup/log mkd400:dka100.bck [.rest...], it returns: %BACKUP-F-OPENIN, error opening MKD400:[000000]DKA100.BCK; as input
-SYSTEM-W-NOSUCHFILE, no such file

What am I missing here?
Thanks,
Mark.
6 REPLIES
Hoff
Honored Contributor

Re: Multiple savesets on a dlt tape

You can restore with BACKUP, or you can use Saveset Manager product to load these back in.

If you're using BACKUP and not COPY, you can just keep executing the following:

$ MOUNT/FOREIGN DKD400:
$ BACKUP MKD400:/SAVE DKE900:[SAVESET1...]
$ BACKUP MKD400:/SAVE DKE900:[SAVESET2...]
...

etc.

This will read off each saveset found on the tape, as the saveset is encountered, and drop the contents into the specified directories on DKE900:. This regardless of the saveset name on the tape.

If you want to see what filenames were used, MOUNT/OVER=ID MKD400:
DIRECTORY MKD400:[000000]

If FWIW you are using COPY here to transfer files off tape, use it with caution. COPY doesn't do tape continuation volumes, and doesn't deal with tape-level processing.

The use of /IGNORE=INTERLOCK does mean that files within the saveset contents might be corrupt; that's a best-effort transfer, and conflicts and errors aren't necessarily logged.

Stephen Hoffman
HoffmanLabs LLC


MarkOfAus
Valued Contributor

Re: Multiple savesets on a dlt tape

Hoff,
Thanks for that.

I apologise, I left off an important fact. I wish to extract from the tape only the 3rd saveset, for example, therefore skipping the arduous procedure of waiting for the tape to restore GiBs of data.

I can restore using /select=blah_blah, but I was wondering what the procedure is to get a particular saveset in isolation?
Jon Pinkley
Honored Contributor
Solution

Re: Multiple savesets on a dlt tape

MarkOfAus
>>> -----------------------------------------------------------------------
I wish to extract from the tape only the 3rd saveset, for example, therefore skipping the arduous procedure of waiting for the tape to restore GiBs of data.

I can restore using /select=blah_blah, but I was wondering what the procedure is to get a particular saveset in isolation?
-------------------------------------------------------------<<<

Are you sure the saveset name is dka100.bck ? As Hoff said, you can do a directory of the tape to see the saveset names

This works for me (AXP VMS 7.3-2 and also worked in VMS 7.2-2) I think it should work with any recent version of VMS.

With privs:

$ set magtape/fast_skip=always MKD400: (This only needs to be done once per boot)

Using the fast skip really makes a lot of difference when you want to skip to the 40th saveset on a tape!


$ mou/for/nounl mkd400:
$! if save_set_number > 2
$ files_to_skip = save_set_number*3-4 ! number of file marks to skip (save_set_number starts with 1, not 0)
$ set magtape/skip=files:'files_to_skip' ! much quicker than reading to find the file name, if you know save set #
$! To position to 3rd saveset, "set mag/skip=files:5" This positions the tape so the next saveset will be the 3rd
$ backup mkd400: disk:[directory...] ! etc. Don't specify file name, and it will use whatever is there.

Jon
it depends
Steven Schweda
Honored Contributor

Re: Multiple savesets on a dlt tape

> What am I missing here?

At the least, a clear explanation of what's
on the tape(s), and what you would like to do
with those data.

"BACKUP /LIST /REWIND tape_device" can show
you the first save set, and then, without the
"/REWIND", it can show you the others. (It
will do an implicit MOUNT /FOREIGN if needed,
so you could skip that step.)

> [...] backup/log mkd400:dka100.bck [...]

Is there a save set named "dka100.bck" on the
tape? (What does BACKUP /LIST say?) Can we
assume that there was a lot of futile tape
reading before that error message appeared?

If you know that you want the third save set,
but you don't know its name, you can use
repeated BACKUP /LIST commands to skip past
preceding save sets, and then use a normal
BACKUP command to do whatever with the Nth
save set.
MarkOfAus
Valued Contributor

Re: Multiple savesets on a dlt tape

Jon,
Yes I am sure dka100.bck is on the tape as I have used COPY to grab it from the tape.
VMS is 7.2-H1 Alpha.

I will take the fast_skip on board, thanks.

I tried the skip files on set magtape, but unfortunately I started the offset at 0, not 1.

You're a genius! :-)
Brilliant!!! I thought I was going mad (I may still be, but that's another issue).

Thanks,
Mark.
MarkOfAus
Valued Contributor

Re: Multiple savesets on a dlt tape

Thanks to Jon for his answer.
$ set magtape/skip=files:5
positions to the correct saveset.