How to Abort tctl command
Frank Sandy
drive, and then realize you need to rewind and start over, how can you
abort the command. Neither ^C nor kill -9 will stop a tctl process
until the tape positioning is finished, which may take 10 minutes or
more.
Is there a way to reset the tape drive? I'd rather not try
anything as drastic as turning off the power on the drive for fear
of damaging the tape.
--
Frank Sandy fsa...@tiac.net
Hamish Marson
> In article <3fe8ch$2...@max.tiac.net>, Frank Sandy <fsa...@max.tiac.net> wrote:
> > If you issue a command like tctl fsf 8 to reposition a tape
> >drive, and then realize you need to rewind and start over, how can you
> >abort the command. Neither ^C nor kill -9 will stop a tctl process
> >until the tape positioning is finished, which may take 10 minutes or
> >more.
> >
> My understanding of this is that it is a BAD THING to get impatient with
> a tape drive. One ^C, and then wait. Second (and third and fourth) interrupts
> kill the initial interrupt, and leave a bunch of child processes hanging around
> that own the device. So short of a reboot, nobody else can then use it.
Sometime before 3.2.5 the tape device was broken, in that if you killed
a process reading from the tape-drive, then sometimes the tape driver
would sit in a piece of code forever waiting for some condition that
never happened... (I had a complete explanation at the time, but I
don't think I still have it).
The problem was fixed in 3.2.5, and I have never seen it happen again.
It used to hit me at least once a week on our backup server which ment
uptime was not something that grew very much. (I got rather angry one day
when I had to reboot 3 times for a stuck tape drive....
--
======================================================================
| Hamish Marson |
| Systems Programmer | |
| Computer Services | INTERNET h.ma...@waikato.ac.nz |
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| New Zealand | FAX +64 7 8384066 |
===========Disclaimer :- Remember. You heard it here first.===========
Tom Griffing
>wrote:
>> > If you issue a command like tctl fsf 8 to reposition a tape
>> >drive, and then realize you need to rewind and start over, how can you
>> >abort the command. Neither ^C nor kill -9 will stop a tctl process
>> >until the tape positioning is finished, which may take 10 minutes or
>> >more.
>> >
>> > Is there a way to reset the tape drive?...
You don't really want to reset the drive itself, but the
tctl process. If the tape is in the middle of a retension
or a rewind, you don't want to interrupt it. Even if the
drive is in the process of advancing to the next file mark,
interrupting it is asking for trouble.
Now, if you've told the tctl command to advance the tape
drive forward 8 file marks and decide otherwise, you want
to stop the tctl command from issuing any remaining
commands to the tape drive telling it to skip forward.
Killing it should do the job, and it will stop once the drive
has finished its current command. Oh ... another thing:
if you have specified a rewind-device, you will also have
to wait for the drive to finish rewinding. But ... then
again, you'd have to rewind it for the next command,
anyway.
All things considered, it's best to be patient with tape
drives.
Hope this helps,
_______________________________________________________________________________
/ Thomas L. Griffing t...@metronet.com (214) 352-3441 /
/ HomePage: http://www.metronet.com:70/9/HomePages/tom/homepage.html /
(______________________________________________________________________/
John DeDourek
<doug@.interramp.com> wrote:
>Until AIX develops a way to gracefully interrupt this, you best be patient...
My experience with interrupting a tar from a !%)MB (oops, I meant 150MB :-)
1/4" tape drive, was that the drive went into an infinite loop (YES the
drive) winding the tape back and forth and I actually had to power down
(rebooting didn't help) to make the tape stop moving.
Yech!
John DeDourek
Ruth Milner
Tom Griffing <t...@feenix.metronet.com> wrote:
>
>Now, if you've told the tctl command to advance the tape
>drive forward 8 file marks and decide otherwise, you want
>to stop the tctl command from issuing any remaining
>commands to the tape drive telling it to skip forward.
Is this how the driver (probably not tctl itself) actually works? Does
it tell the drive n times to skip one file? Or is it smart enough to
know that some types of tape drive can skip multiple files, so that it
only needs to say "skip n files"?
If it does the latter, then you're stuck waiting until the tape
finishes that. While this might seem like the poorer of the two
behavior options, many tape drives skip much faster if they don't
have to pause at every filemark.
I agree 100% about being patient with tape drives! We use tapes really
heavily here, and it's really easy to screw yourself by getting mad
at them. :-)
--
Ruth Milner NRAO Socorro NM
Manager of Computing Systems rmi...@aoc.nrao.edu