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Who has the Lock??
Message
De
17/07/2000 09:42:34
Jon Nelson
Trader Systems Limited
Reading, Royaume Uni
 
 
À
17/07/2000 09:19:27
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Divers
Thread ID:
00393015
Message ID:
00393224
Vues:
30
Doug,

Altering the table structure and wrapping the RLOCK/UNLOCK functions is an option but I would prefere not to alter the prodction table structure....

If VFP is taking care of the locking it must be done at the file level... therefore it must be writing locking information to the database header or flagging each record??? I've been digging around for some info on the DBF file structure (e.g. http://www.e-bachmann.dk/docs/xbase.htm) and there are several areas marked as 'reserved' - do you know of a comprehensive document on VFP file structure with regard to record locking?

Many thanks


Jon Nelson

>Jon,
>
>I doubt that you'll find that information inside of the O/S as it is managed by VFP itself. You might go over to www.hallogram.com and see if they have any API libraries that could help.
>
>Other than that you'll need to roll your own. It's not too difficult - all you need is a table that contains some basic information like:
>
>User's Name
>Table Name
>Record Number
>Date & Time of lock
>
>etc... With this you can build your own locking semaphore table and then 'wrap' your RLOCKS with it.
>
>Best,
>
>DD
>
>>Doug,
>>
>>I've tried the usual Server manager - this shows open files but not FLOCK and RLOCKS.... Are you aware of any other tools (Perfomance Monitor/Resource Kit..)?
>>
>>Cheers
>>
>>Jon Nelson
>>
>>>>I'm trying to resolve a deadlock situation on a multi-user VFP database using free tables.
>>>>
>>>>Is anyone aware of any tools (running on an NT Server) that show which user (at a connected workstation) has a record/file lock on a table? Ideally I would like to be able to see that user X has table name YYY open at workstation ZZZ with a record number NNNN locked...
>>>>
>>>>
>>>>I've spent some time digging around trying to find info on this and have looked at Win API NetFileEnum - but this seems to be a dead end...
>>>>
>>>>Any information on exactly how record locks are applied at a low level would be appreciated (is this to the actual DBF file or is this done using some other operating system mechanism)???
>>>>
>>>>TIA
>>>>
>>>>Jon Nelson
>>>
>>>
>>>Jim,
>>>
>>>Well, you can look at the System Tools stuff built in and find out who has what resources open but programatically I don't really know off hand.
>>>
>>>Check out Communications Horizons. Neil Weicher usually has something that works. Bright guy.
>>>
>>>Best,
>>>
>>>DD
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