The logical disk utility is a system management tool available
 	to any user for controlling logical disk usage.

 	A Logical Disk is a file available on a Physical Disk, which
 	acts as a real Physical Disk (the file may or may not be
 	contiguous). The Logical Disks are available in any directory
 	of the Physical Disk.

 	A large disk can be divided into smaller sections, each a Logi-
 	cal Disk, supporting the same I/O functions as the Physical Disk.
 	By giving the Logical Disk File a good  protection level and
 	mounting it private or with device protection, you are able to
 	add a number of protection levels to your file system.

 	The logical disk is controlled by the LD utility, which can
 	be directly invoked from DCL.

 	Format:

 	LD [/qualifiers] [Filespec] [Device]

 	Starting with V9.0 LD can also treat files on disk as a tape
 	(Logical Magtape, a.k. LM). all commands are the same as for LD,
 	but instead of LD one needs to use the LM command.