Using File Locking and Record Locking in FoxPro

• Microsoft Visual FoxPro for Windows, version 3.0
• Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, and 2.5a
• Microsoft FoxPro for Windows, versions 2.5 and 2.5a

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