PRB: "The database must be opened exclusively" Multiuser Error

• Microsoft Visual FoxPro for Windows, versions 3.0, 5.0, 5.0a

SYMPTOMS

In a multiuser situation, when you perform tasks that affect the contents of a database (.DBC file), the error "The database must be opened exclusively" is displayed.

CAUSE

The command requires exclusive access to the database. Several commands that create or modify database objects require that the database not be shared--at design time or run time.

This error may also occur at run time in an application or EXE if you have included the database(s) in the project. By including the database(s) in the project, you have caused them to be read-only, and you will not be able to properly validate the database. In this situation, it is possible for ISE CLUSIVE() to return a .T. (true) value and still get the error message described above.

WORKAROUND

If you receive the error "The database must be opened exclusively" at design time, all developers must close the database before you can proceed.

To prevent this error from occurring at run time when manipulating views or connections, create a local database for each user. All users will have exclusive access to their database, and will also be able to update the table records contained in a centralized, shared database.

To verify whether or not a database is open exclusively, use the ISEXCLUSIVE() function. The syntax for the ISEXCLUSIVE() function is:

   ISEXCLUSIVE([cTableAlias | nWorkArea | cDatabaseName [, nType]])

   CLOSE ALL
   OPEN DATABASE SYS(2004)+"SAMPLES\DATA\TESTDATA"
   SELECT 0
   USE CUSTOMER
   IF ISEXCLUSIVE('testdata',2)
      INDEX ON CITY TAG CITY
      ELSE
      =MESSAGEBOX("Database must be opened Exclusively")
   ENDIF
   CLOSE DATABASE

   SET DATABASE TO <dbc name>
   CLOSE DATABASE
   OPEN DATABASE <dbc name> EXCLUSIVE

STATUS

This behavior is by design.

MORE INFORMATION

If a view or a table contained in a database is open for shared use, the database is also shared. Therefore, all multiuser applications require that a database be shared.

However, commands that directly relate to the database (.DBC file) structure and commands that involve the creation or deletion of objects require exclusive use of the database. These commands include:

   CREATE TABLE
   MODIFY STRUCTURE
   ALTER TABLE
   ADD TABLE
   RENAME TABLE

   CREATE SQL VIEW
   MODIFY VIEW
   DELETE VIEW
   RENAME VIEW

   CREATE CONNECTION
   MODIFY CONNECTION
   DELETE CONNECTION
   RENAME CONNECTION

   INDEX ON         && You can however use INDEX ON on a view
   DELETE TAG

   CREATE TRIGGER
   DELETE TRIGGER

   APPEND PROCEDURES
   COPY PROCEDURES
   MODIFY PROCEDURE

   COMPILE DATABASE
   PACK DATABASE
   VALIDATE DATABASE