On Mon, Jul 12, 2004 at 05:34:16PM -0400, Craig Steinberger wrote:
> Using the stream numbers for the bpend process will not work, since
> you can't predict which streams will end first. Say you have 5
> streams, and stream #2 takes the longest. How do you know which one
> should restart the database?
> 
> Typically what is done is have the scripts keep a counter of some
> sort, and when each stream ends it decreases the counter. You have to
> be careful of race conditions on the counter file (if that's how you
> implement it), and of automatic reruns in case of errors.

You also have to be careful of what happens if your last stream fails
so you don't leave your database in hot backup mode.  In the rerun case,
you could put your database in hot backup mode and never take it out
because there is only 1 stream.  Alternatively, we've cases where the
database never went into hot backup mode in the first place.  Add to all
that the complexity of making sure you really do have all your archive
logs and you begin to see how hard the problem just might be.

Frankly, if you're trying to do your own version of a database agent,
give up.  The aggravation simply isn't worth it.  No matter how hard you
try, you will have days when you won't be able to recover.  Something
always seems to happen and it will be the event you haven't anticipated
(today for us was a master server crash in the middle of a vault eject 
run).

        .../Ed

-- 
Ed Wilts, Mounds View, MN, USA
mailto:ewilts AT ewilts DOT org