[AccessD] notes on mdb bloat

...where is Jurgen when we need him? ...this is right up his alley :(

William Hindman "My idea of an agreeable person is a person who agrees with
me." Disraeli

----- Original Message ----- 
From: "Gustav Brock" <gustav at cactus.dk>
To: "Access Developers discussion and problem solving"
<accessd at databaseadvisors.com>
Sent: Wednesday, March 03, 2004 1:06 PM
Subject: Re: [AccessD] notes on mdb bloat


> Hi Jim
>
> >   My guess would be no.  Note that Garry mentions that it stays bloated
> > until compact.  That doesn't make sense.  If the record locking
algorithm
> > can work after the database is compacted, then why would it have to
bloat it
> > in the first place?  It just doesn't make sense from that standpoint.
>
> It could if you assume that - after compacting, when a record is opened
> for editing - it will be copied as a new and saved while the old is
> marked as deleted. But as you say, just guessing.
>
> >   It does make sense though as to how they could achieve it with little
> > problem, as they are just duplicating a technique that many developers
used
> > to get pseudo record level locking.  It would be a simple matter to
change
> > the add logic to always use an empty page (they in part had already done
> > that for JET 3.5).
>
> >   So there's another reason why it's probably not that; if it were that
> > simple (one record per page), then why did we need a new version of JET?
> > Seems like something they could have put in A95 or A97 quite easily.
>
> Well, the implementation is slightly more complicated than bloating a
> row to fill a page. If I understand the article(s), the revised Jet
> engine maintains a flag which is set when any user requests row-level
> locking which forces subsequent users also to use row-level locking
> even if their default setting was for page-level locking.
>
> >   With no docs, it's all guess work though.
>
> Yes, true. However, experimenting with this while watching the mdb file
> with an hex viewer/editor could tell a lot. I have neither the time
> nor the need for this, though ...
>
> /gustav
>
>
>
> > -----Original Message-----
> > From: accessd-bounces at databaseadvisors.com
> > [mailto:accessd-bounces at databaseadvisors.com]On Behalf Of Gustav Brock
> > Sent: Wednesday, March 03, 2004 12:11 PM
> > To: Access Developers discussion and problem solving
> > Subject: Re: [AccessD] notes on mdb bloat
>
>
> > Hi all
>
> > Does this - simplified - boil down to, that all row-level locking does
> > compared to page-level locking is bloating a row to fill a page?
>
> > /gustav
>
>
> >> Hi Seth et all
>
> >> In Garry Robinson's newsletter I noted this extremely interesting
topic:
>
>
> >> SINGLE RECORD LOCKING, BLOAT AND CITRIX BUGS
>
> >> Did you know that the record-level locking option (menu
> >> Tools~Options~Advanced) that is used by Access 2000 onwards has an
> >> interesting twist. To achieve a single record lock, each record that
> >> is locked uses up all of an Access page in the mdb file. This page of
> >> data, most of which will probably be empty for records with only a few
> >> fields, consumes 4000 bytes. This space is later recovered when the
> >> database is compacted but if you have a database that seems to expand
> >> fast, this could be your culprit. For more on this database bloat and
> >> a possible cure for Access corruptions for Citrix head to this page.
>
> >> http://ewbi.blogs.com/develops/2004/01/access_corrupti.html
>
> >> and an other blog on the same topic
> >> http://dbforums.com/arch/213/2002/10/551337
>
> >> Gary is here:
>
> >> http://www.vb123.com/
>
> >> /gustav
>
>
> >>> I hadn't even thought of that.  I tried it just now, and the resulting
> >>> mdb is 1.5MB.  Still three times as big as the A97 version, but not as
> >>> big as the base A2K version.
>
> >>> The unicode comments make sense, I had forgotten about that, too.
>
> >>> Oh well, more interesting info from the developer front...
>
> >>> Seth
>
> >>> On Wed, 2003-03-12 at 11:45, Gustav Brock wrote:
> >>>> Hi Seth
> >>>>
> >>>> What happens if you "forward port" the A97 version to A2000?
> >>>>
> >>>> /gustav
>
> -- 
> _______________________________________________
> AccessD mailing list
> AccessD at databaseadvisors.com
> http://databaseadvisors.com/mailman/listinfo/accessd
> Website: http://www.databaseadvisors.com
>