HP 3000 Manuals HP 3000 Manuals
Multiple Record Locking A program that specifies multiple record locking for a file can simultaneously hold several record locks. This prevents other programs from accessing these locked records but does not deny them access to any records that are not locked. Multiple record locks for a program can be acquired in either of two ways: manually or automatically. Manual Multiple Record Locking You can specify automatic single record locking for a file in your program by using the LOCK MODE IS MANUAL WITH LOCK ON MULTIPLE RECORDS clause in the SELECT statement. Your program can acquire a lock by accessing a record with a READ WITH KEPT LOCK statement. If you used the WRITELOCK directive at the time you compiled your program, it acquires a manual multiple record lock whenever it accesses the file with a WRITE or REWRITE statement. These locks are released when your program does one of the following: * closes the file * executes a COMMIT statement * executes a ROLLBACK statement * executes an UNLOCK statement for the file. Automatic Multiple Record Locking You can specify automatic multiple record locking by using the LOCK MODE IS AUTOMATIC WITH LOCK ON MULTIPLE RECORDS clause in the SELECT statement. Your program acquires an automatic multiple record lock whenever it reads a record in the file. If you specified the WRITELOCK directive at the time you compiled your program, it also acquires a lock whenever the program accesses the file with a WRITE or REWRITE statement. The locks are released when your program does one of the following: * closes the file * executes a COMMIT statement * executes a ROLLBACK statement * executes an UNLOCK statement for the file.