Lock() - IVR Programming Command | Xtend IVR Tutorial

Lock ("[name]")

Permits one and only one thread/channel/device to execute inside a block of statements.

Parameters

[name] Name of the lock created.

Remarks

By executing the operation, shared resources ensure that only atomic manipulation is performed on their values.
Lock() creates a mutex by this name and locks it.

Caveat against misuse of this function:

Minimise the lines of code in the Lock()-Unlock() block.
Built-in Expressions, String & Number manipulation functions, Database access and the atomic functions can be used in the block.
Other plugins, sub-functions and voice device dependant commands like Play, Record, Input etc. *SHOULD NOT* be used in code between Lock() and Unlock().
ONSYSTEMERROR and ONRUNTIMEOUT will result in an immediate jump to these labels. Thus all locks of that port will be automatically released and the entire Lock()-Unlock() block *MAY NOT* execute properly. Hence, no function that may result in an ONSYSTEMERROR jump should be used between Lock() and Unlock().
ONHANGUP and ONTIMEOUT labels *DO NOT* take effect when locked.
Coding GOTO or IF THEN GOTO commands after a Lock() will cause an Unlock() of all locks to happen.
All locks are automatically released when HANGUP command is executed.

Example

 
:MAIN 
    .......
    .......
    // The database operation is done inside a lock - unlock block
    // so that only one thread will access it and all other threads
    // will wait in Lock() to get its turn.
    Lock()
    $sql = "select * from EMP where status = 'Q'"
    $result = db.RunSQL($db,$sql)
    if $result = 0
        // query failed.
        Unlock()
        goto MAIN
    endif
    // The field status is modified to 'X' so that this record will not be
    // taken by any other threads.
    $sql = format("update EMP set status = 'X' where AUTOID = %d",$result.AUTOID)
    $stat = db.RunSQL($db,$sql)
    Unlock()
    ........
    ........