Q92345: Using File Locking and Record Locking in FoxPro

Article: Q92345
Product(s): Microsoft FoxPro
Version(s): 2.00 2.50 2.50a | 2.50 2.50a 3.0
Operating System(s): 
Keyword(s): 
Last Modified: 09-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 6.0 
- Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a 
- Microsoft FoxPro for Windows, versions 2.5, 2.5a 
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SUMMARY
=======

When a command requires a file lock and the corresponding file is not already
locked, FoxPro attempts to lock the file. Similarly, when a command requires a
record lock and the corresponding record is not already locked, FoxPro attempts
to lock the record. If the lock attempt is successful, FoxPro executes the
command and releases the lock.

For a list of commands that automatically lock a file or individual records, see
the table below.

Use manual locking commands in the following situations:

- When you are editing a database with the CHANGE or EDIT command and a format
  file.

- When you are editing a database using a memory variable and a command such as
  SCATTER. Note that the GATHER command locks each record as it updates the
  database; however, not locking the record during the editing process can
  introduce data-integrity problems.

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

The following commands automatically lock a file or individual records, as
indicated:

  Command             Type of Locking
  -----------------------------------------------------------------------

  APPEND              Locks current record

  APPEND BLANK        Locks database header (briefly)

  APPEND FROM         Locks entire database


  APPEND FROM ARRAY   Locks database header

  APPEND MEMO         Locks current record

  BROWSE              Locks current record and all records from fields in
                      related databases (specified by an alias) once the
                      user begins editing a field

  CHANGE (without a   Locks current record and all records from fields in
  format file)        related databases (specified by an alias) once the
                      user begins editing a field

  DELETE              Locks current record

  DELETE NEXT 1       Locks current record

  DELETE RECORD <n>   Locks record <n>

  DELETE <scope       Locks entire database
  beyond one>

  EDIT (without a     Locks current record and all records from fields in
  format file)        related databases (specified by an alias) once the
                      user begins editing a field

  GATHER              Locks current record

  INSERT-SQL          Locks database header

  MODIFY MEMO         Locks current record when editing begins

  READ                Locks current record (and all records from aliased
                      fields)

  RECALL              Locks current record

  RECALL NEXT 1       Locks current record

  RECALL RECORD <n>   Locks record <n>

  RECALL <scope       Locks entire database
  beyond one>

  REPLACE             Locks current record (and all records from aliased
                      fields)

  REPLACE NEXT 1      Locks current record (and all records from aliased
                      fields)

  REPLACE RECORD <n>  Locks record <n> (and all records from aliased
                      fields)

  REPLACE <scope      Locks entire database (and all files from aliased
  beyond one>         fields)

  SHOW GETS           Locks current record (and all records from aliased
                      fields)

  UPDATE              Locks entire database

Additional query words: VFoxWin FoxDos FoxWin 2.x multi-user kbvfp300 kbvfp500 6 6 multiuser network networking automatic

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro200DOS kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro250 kbFoxPro250a kbVFP300 kbVFP500 kbVFP600
Version           : 2.00 2.50 2.50a | 2.50 2.50a 3.0

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