[bknr-devel] SBCL and OpenMCL ports done properly

[Hans Hübner]

2006/2/7, Kamen TOMOV <ktomov at web.de>:
> On Tue, Feb 07 2006, Hans Hübner wrote:
>
> > ..
> > I will propably work on database maintenance and operations so that
> > BKNR based systems can be run for a long time without much nursery.
>
> What kind of nursery do you mean?
>
> > The snapshotting mechanism currently eats disk space without bounds,
>
> It seems to me it eats as much as necessary - no more no less. Or am I
> missing something?

If you regularily snapshot from a cron job, all snapshots will be kept
on disk and need to be manually moved to offline media.  Depending on
the transaction rate, it may be neccessary to snapshot often, which
will use a lot of disk space.  It would be good if the Datastore would
provide an automatic mechanism that purges older snapshots.  This
could be done on a simple (only keep N snapshots) or a more complex
basis (keep the last three snapshots, one for each week, one for each
month or some such).

Also, a restore tool is needed that helps selecting a snapshot to
restore.  I have been bitten many times while selecting an older
snapshot to restore and selecting a too-early one.  Instead of
manually having to select a certain snapshot, one should be able to
specify a date and time (or manually created markpoint) to restore to
and have the environment select the right snapshot file and
rollforward location.

It would also be good if a snapshot could be automatically created as
soon as a certain restore time limit has been reached.  This would
require adding up the execution time of restored and newly executed
transactions and scheduling a snapshot only if it is required. 
Together with the automatic selection of a snapshot to restore, this
would make the database system much easier to use, and it would also
help with the disk growth problem.

> > and the blob garbage collection is not automated.
>
> What exactly do you mean? If we delete blob wouldn't the memory be
> cleaned?

Yes.  Blob files cannot be deleted when the blob object is deleted
because they may be needed again, should the user decide to restore an
earlier snapshot.  An integrated snapsht archival function would be
able to move deleted blobs offline together with the corresponding
snapshot file and transaction log.  At the moment, there is the
(bknr.datastore:delete-orphaned-blob-files) function which can be
called to get rid of stray cats.

Cheers,
Hans