Plateforme Level Extreme
Abonnement
Profil corporatif
Produits & Services
Support
Légal
English
Why this DELETE is so slow?
Message
 
À
21/02/2005 19:52:53
Walter Meester
HoogkarspelPays-Bas
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Versions des environnements
Visual FoxPro:
VFP 8 SP1
OS:
Windows 2000 SP4
Network:
Windows 2003 Server
Database:
Visual FoxPro
Divers
Thread ID:
00988740
Message ID:
00989100
Vues:
41
Hi Walter,

What you are saying about the file server behaviour is probably true. But how come the updates are slow *only* if they involve nested select (at least it's my observation)?
If the issue is with write and read caching, then shouldn't it also be slow for the following:
DELETE FROM resource WHERE "whatever_condition_on_resource_table_only" ???

No, there is no ref integrity going on.

I assume Filemon should be running on the File Server. If yes, then unfortunately I can't use it. At least not now.

--Andrew


>Hi andrew,

>This is actually normal behaviour. When only one instance is using the tables, the file >server can use read and write buffering on the tables.

>When a second instance is opening the same tables, the server is going to disable at >least the write cache. As soon you are going to write something to the table it is also >going to disable the read chache. This file server mechanism is called opportunistic >locking and is part of the file server redirector implementation.

>Question. Is there any referential integrity in effect (cascading deletes perhaps)?

>You can download filemon from www.sysinternals.com to see what messages go accross the >network and you can find out what is taking so long. Also you can see what information >comes from the cache and what is read from/written to the network.

>Walter
Précédent
Suivant
Répondre
Fil
Voir

Click here to load this message in the networking platform