Experimental Physics and
Industrial Control System

"Kasemir, Kay" <[email protected]> · Thu, 05 Jun 2008 16:00:18 -0400

> We start the Archive Daemon on boot in /etc/rc.local.  As engine lock
> files will be left after a power failure, for example, it's tempting
> to first remove any remaining archive_active.lck files.  However, the
> Channel Archiver manual warns against blindly removing these lock
> files before backing up and testing the data files.
> 
> Is looking at any given PV using ArchiveExport an appropriate test to
> ensure the data files are not corrupt, or is some other test
> recommended?

> Should it be safe to remove archive_active.lck files before starting
> the ArchiveDaemon in /etc/rc.local?
Probably.

Since this is after a reboot, you don't have to worry about another
engine still being active in the same directory, and can remove
that lock file.

There is of course the worry about corrupt files,
for which there is no good answer.
Looking at one channel or using the 'test' option of the ArchiveDataTool
can make you feel better, but the binary archive files are no
equivalent to a relational database with re-do logs or the like
which are supposed to keep your data safe.

-Kay

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System