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Why did FLUSH solve this problem?
Message
From
09/05/2001 15:25:51
 
 
To
09/05/2001 15:09:29
General information
Forum:
Visual FoxPro
Category:
FoxPro 2.x
Miscellaneous
Thread ID:
00505050
Message ID:
00505497
Views:
31
>>>>As for buffering on the server, never...ever... use write caching on the server unless the disk controller is specially designed to work with databases. This advice is not just for Fox data. I've been reading SQL Server Books Online lately and that warning is all over in there.
>>>
>>>In your experience, what are the drive controller manufacturers whose products have been "specially designed to work with databases"?
>>
>>I can't say I know of one above another. Just what the docs are saying.
>
>OIC... so MS is basically saying, don't use a disk controller with SQL Server unless we've approved it. I wonder how one does that...
>

No. They don't list any brands or models. It's basically a warning that if you do use write caching, that it can corrupt your data. I've seen this with VFP.

>>>It's a bad idea to extrapolate SQL Server to all back-end or file-server databases. All applications, not just databases, are supposed to delegate file I/O to the OS; most have no other choice. However, SQL Server enjoys a (too?) close relationship to NT/W2K and uses a lot of tricks to improve performance. It's not surprising the SQL Server docs are littered with warnings.
>>
>>Issues are different with databases apps as opposed to non-database apps. Word, for example, pulls the entire document into memory. Database apps inheritly have problems with write caching because of what they do.
>
>Like what?

- Person A edits a record, then saves changes. Person B retrieves the record, but doesn't see the changes.

- Person A adds a new record. The insert code does a lookup in a table to get the next Primary Key, then increments the counter in the field. Person B then does the same thing. However, because the writes from person A are cached, person B gets the same key.
Craig Berntson
MCSD, Microsoft .Net MVP, Grape City Community Influencer
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