We have the same issue.  In our case, it's caused by a corrupt or
mismatched dscenu.txt file, causing "ANS0106E message index not found for
message..." in dsmerror.log.

To fix it, we stop the TSM scheduler (no need for that if you're using CAD
I guess), replace the dscenu.txt file with a good one from a client that is
NOT giving you RC 12s, and restart the scheduler. Works for us anyway.
--------------------
Lindsay Morris
CEO, TSMworks
Tel. 1-859-539-9900
lindsay AT tsmworks DOT com


On Fri, Aug 26, 2011 at 12:37 PM, Andrew Raibeck <storman AT us.ibm DOT com> 
wrote:

> An in-use file should not cause an RC 12. Either you are running an old
> client level with some defect that issues the wrong return code (for
> example, see go to the URL in my sig and search for IC35763); or there is
> some additional error being thrown that causes the RC to be set to 12.
> Examine your dsmerror.log and dsmsched.log files very carefully for any
> other ANSnnnnE or ANSnnnnS messages that might trigger the RC 12. Also, see
> my other recent posts on this topic.
>
> Best regards,
>
> Andy Raibeck
> IBM Software Group
> Tivoli Storage Manager Client Product Development
> Level 3 Team Lead
> Internal Notes e-mail: Andrew Raibeck/Hartford/IBM@IBMUS
> Internet e-mail: storman AT us.ibm DOT com
>
> IBM Tivoli Storage Manager support web page:
>
> http://www.ibm.com/support/entry/portal/Overview/Software/Tivoli/Tivoli_Storage_Manager
>
> "ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu> wrote on 2011-08-25
> 09:26:24:
>
> > From: Jimou <tsm-forum AT BACKUPCENTRAL DOT COM>
> > To: ADSM-L AT vm.marist DOT edu
> > Date: 2011-08-26 12:15
> > Subject: Ang: Re: Help tracking down spurious "Failed 12"
> > Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT vm.marist DOT edu>
> >
> > Hi
> > I wonder why we can have a RC =12 for a skipped file in use,
> > cause there http://www.dsi.upmc.fr/dsi/doc/stockage/clients-tsm/
> > tsmwin/ans60012.htm
> > i see that it should be RC=4
> >
> > But i also have a RC=12 and the only message i got is "in used file".
> >
> > Someone could explain to me why it is not a RC=4 ??
> > Ty in advance.
> >
> > +----------------------------------------------------------------------
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>