Interrupt 21h Function 440Dh Minor Code 4Ah 

Locks the logical volume. 

mov ax, 440Dh        ; generic IOCTL

mov bh, LockLevel    ; see below

mov bl, DriveNum     ; see below

mov ch, 08h          ; device category (must be 08h)

mov cl, 4Ah          ; Lock Logical Volume

mov dx, Permissions  ; see below

int 21h

jc error

Parameters

LockLevel

Level of the lock. This parameter must be either 0, 1, 2, or 3.

DriveNum

Drive to lock. This parameter can be 0 for the default drive, 1 for A, 2 for B, and so on.

Permissions

Operations that the system permits while the volume is locked. This parameter is specified only when a level 1 lock is obtained or when a level 0 lock is obtained for the second time for formatting the volume. For other lock levels, this parameter is zero. When a level 1 lock is obtained, bits 0 and 1 of this parameter specify whether the system permits write operations, new file mappings, or both by other processes during a level 1 lock as well as during level 2 and 3 locks. If this parameter specifies that write operations, new file mappings, or both are failed, these operations are failed during level 1, 2, and 3 locks. This parameter has the following form:

Return Value

Clears the carry flag if successful. Otherwise, the function sets the carry flag and sets the AX register to an error value.

Remarks

The volume must be locked before the application performs direct disk write operations by using Interrupt 26h or the IOCTL control functions. Lock Physical Volume (Interrupt 21h Function 440Dh Minor Code 4Bh306_5U) is used instead of this function before a call to an Interrupt 13h function. Unlock Logical Volume (Interrupt 21h Function 440Dh Minor Code 6Ah24UZ_OZ) should be used to release the lock.