Re: Problem browsing large file
From: Ook (MSNews_at_emberts.UpYoursSpammer.emberts.com)
Date: 03/18/04
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Date: Wed, 17 Mar 2004 18:24:25 -0700
The plot thickens. I have another app that keeps this file open 24/7. If I
open the file NOUPDATE with VFP7/8, it pauses for a minute, and then the
24/7 app throws an error (table in use). What is extremely weird is that
this error bypasses the error trap!
It appears that by opening the file, VFP is trying to write to is, even
though I've opened it NOUPDATE. I'm wondering if VFP is detecting something
wrong with file or the index, and is trying to automatically correct it?
Also, how can table in use error bypass the error trap like that?
"Cindy Winegarden" <cindy.winegarden@mvps.org> wrote in message
news:uZSmdcDDEHA.3608@TK2MSFTNGP10.phx.gbl...
> In news: %236b8oODDEHA.1588@tk2msftngp13.phx.gbl,
> Ook <outlookexpress@nospam@embertsdotcom> wrote:
> > Update - If I set DELETED OFF, the problem goes away. I'm thinking
> > that the tag on DELETED() is somehow causing this - should you not
> > create an index on DELETED() with large tables?
>
> Hi Ook,
>
> FoxPro's Rushmore technology can be a help or a hindrance, and only
testing
> in your environment can decide for you, as you've discovered. I assume
that
> when you open the table FoxPro will read the DELETED() index and then go
> back to fetch records that qualify - i.e. records that are not deleted.
> Since your table is large Fox has to read a rather large index before
> opening the table. Without the index Fox probably fetches all the records
> and then filters out the deleted records locally.
>
> In general, indexes on fields with only a few discrete values (Sex is
> another one) should be tested to see whether they help or hinder in your
> environment.
>
> There was an excellent article about this by Chris Probst in the May, 1999
> issue of FoxPro Advisor magazine.
>
> --
> Cindy Winegarden MCSD, Microsoft Visual FoxPro MVP
> cindy.winegarden@mvps.org www.cindywinegarden.com
>
>
>
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