[comp.databases] Record Locking in foxplus+ SCO xenix

zureick@ucunix.san.uc.edu (John H. Zureick) (05/16/91)

Is there any software avaiable that allows more sophisticated record
locking than is available in Foxplus?  For instance, I would like to
take multiple records from a file, load them into an array, and allow
a user to edit them.  As the user is editing them, I don't want these
records to be available to other users except on a read-only basis.

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John H. Zureick					zureick@ucunix.san.uc.edu

timk@wynnds.xenitec.on.ca (Tim Kuehn) (05/16/91)

In article <1991May15.201457.14019@ucunix.san.uc.edu> zureick@ucunix.san.uc.edu (John H. Zureick) writes:
>Is there any software avaiable that allows more sophisticated record
>locking than is available in Foxplus?  For instance, I would like to
>take multiple records from a file, load them into an array, and allow
>a user to edit them.  As the user is editing them, I don't want these
>records to be available to other users except on a read-only basis.

Then why not use the rlock() function call? The only possible problem 
you may have is deadlocking, where two applications have locked records
the other application wants and they both try to lock something someone
else already has after locking records other applications want to get at. 

For example 
process #1 wants to lock records 1,2,3; 
process #2 wants to lock records 2,3,4;

#1 locks 1, tries to lock 2, can't so it locks 3, then tries to lock 2 again.
#2 locks 2, tries to lock 3, but can't, so it locks 4, then tries to lock 3. 

Both processes are now deadlocked. This is something to look out for. 

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pew@cs.brown.edu (Peter E. Wagner) (05/16/91)

In article <1991May15.201457.14019@ucunix.san.uc.edu>, zureick@ucunix.san.uc.edu (John H. Zureick) writes:
|> Is there any software avaiable that allows more sophisticated record
|> locking than is available in Foxplus?  For instance, I would like to
|> take multiple records from a file, load them into an array, and allow
|> a user to edit them.  As the user is editing them, I don't want these
|> records to be available to other users except on a read-only basis.

FoxPro, Foxbase's big brother, allows this.

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Peter E. Wagner          (401)863-7685        pew@cs.brown.edu
Department Computer Science   Box 1910        pew@BROWNCS.BITNET
Brown University, Providence, RI 02912        uunet!brunix!pew

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