DOCUMENT:Q151841  21-AUG-1999  [foxpro]
TITLE   :PRB: FoxPro and Clipper Share the Same DBF Files on a Network
PRODUCT :Microsoft FoxPro
PROD/VER:2.50 2.50a 2.50b 2.60 2.60a 3.00
OPER/SYS:
KEYWORDS:kb3rdparty

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The information in this article applies to:

 - Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a 
 - Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.5b, 2.6, 2.6a 
 - Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b 
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SYMPTOMS
========

RLOCK() will not function properly when a FoxPro Application and a Clipper
Application access the same table simultaneously.

CAUSE
=====

Both FoxPro and Clipper have their own Locking Mechanism. When applying a lock
to a table file on the Network, the function FLOCK() can be recognized by both
Foxpro and Clipper; it will return a TRUE (.T.) if the table is locked by any of
the applications. The function RLOCK() returns a TRUE only if a particular
record of a table is locked by the same application. In other words, if a record
was locked by Foxpro, Clipper can still lock the particular record without an
error, and it has the same behavior the other way around.

RESOLUTION
==========

Use FLOCK() instead of RLOCK().

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

Run the following code in Clipper:

      ** <Table_Field> is a numeric field in a Table

      USE <Table_Name> SHARED
      GOTO TOP
      REPLACE <Table_Field> WITH 100   && Initial Value of <Table_Field>

      DO WHILE RLOCK()                 && Record is Locked by Clipper
         ? <Table_Field>
         WAIT ?Hit a Key ...? TO M.temp
      ENDDO

and Run the following code in FoxPro:

      USE <Table_Name> SHARED
      GOTO TOP

      DO WHILE RLOCK()                 && Record is Locked by Foxpro
         REPLACE <Table_Field> WITH <Table_Field> + 1
         WAIT ?Hit a Key ...? TO M.temp
      ENDDO

Expected Behavior
-----------------

When the above code is executed by Foxpro and Clipper at the same time, the
expected behavior is:

 - Clipper locks the record and displays the value of the field, which is 100.

 - Foxpro cannot lock the same record, so it will keep on trying to lock the
   record and will not be able to add 1 to the field.

Actual Behavior
---------------

 - Clipper locks the record and displays the value of the field, which is 100.

 - FoxPro locks the record successfully and adds 1 to the field.

 - Press a key on the Clipper machine, and it displays 101.

 - Press a key on the Foxpro machine, and it locks the record successfully again
   and adds one more to the field.

 - Press a key on the Clipper machine, and it displays 102.

Additional query words: FoxWin VFoxWin FoxDos

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Keywords          : kb3rdparty 
Technology        : kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro200DOS kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro250bDOS kbFoxPro260DOS kbFoxPro260aDOS kbFoxPro260 kbFoxPro250 kbFoxPro250a kbFoxPro250b kbFoxPro260a kbVFP300 kbVFP300b
Version           : 2.50 2.50a 2.50b 2.60 2.60a 3.00

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