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Pessimistic buffering
Message
De
17/11/2002 17:25:04
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
À
17/11/2002 17:09:14
John Ryan
Captain-Cooker Appreciation Society
Taumata Whakatangi ..., Nouvelle Zélande
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00723655
Message ID:
00723680
Vues:
20
>Hilmar
>
>Of course, if you use a RV then many users can make changes to different fields in the same record without overwriting each others' changes. Should people edit the same field, having the most recent change prevail does make sense.

Well, it may "make sense" to edit different fields in the same record, but it requires a lot of extra work. (Visual Extend does it, though.) Actually, I have tried this with local view and table - I don't know exactly how a remote view against a database server would react, and there might be some differences.

As to having the "most recent change prevail": with pessimistic buffering, the second user can't even edit if the first user has started editing ('cause the record can't be locked). With optimistic buffering, you can select to have the first change prevail, or the last one - this depends on the options you use in TableUpdate().

However, "having the most recent change prevail" can actually be dangerous - because the first user receives no warning that his changes are being overwritten. Using the default options for TableUpdate() is safer, it seems to me, because the second user simply can't overwrite the changes. The second user can still start over, and re-apply the changes to the current record.

Hilmar.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
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