This function disconnects a file or device from a logical disk:

 	Function:	IO$_LD_CONTROL

 	P6 = Subfunction: LDIO$K_DISCONNECT

 	IOSB word 0 = status

 	The subfunctionmodifier LDIO$M_ABORT allows the file to be disconnected
 	regardless of it's state.

 	The following flag is for tape use only:

 	LDIO$M_KEEP	Will disconnect the container file but keep the
 			unit available for reuse.
 	LDIO$M_TRUNCATE	Will truncate the container file to the last written
 			block (valid only of the containerfile was connected
 			with extend enabled).

 	Errors returned:

 	SS$_DEVFOREIGN	Device mounted foreign
 	SS$_DEVMOUNT	Device mounted
 	SS$_BADFILEHDR	Bad logical disk file
 	SS$_DEVASSIGN	Device still active (reference count > 0)
 	SS$_DEVINACT	Device not connected
 	SS$_FORMAT	FCB specified in SBK is invalid
 	SS$_ACCVIO      SBK block cannot be read
 	SS$_NORMAL	Successful completion

 	Other possible errors are errors returned by the lockmanager.