Overview

IN CLASSICAL TERMS, A DEVICE is a hardware component attached to a computer for purposes of data storage or input/output. Such devices include disk drives, magnetic tape drives, printers, terminals, and so on. In the OpenVMS environment, the term device includes all these hardware components, along with virtual devices created by the OpenVMS software. Examples of virtual devices are the mailboxes used for interprocess communication, DECterm windows on VAXstation and AlphaStation monitors, and a shadowset disk device.

The purpose of some devices, particularly disk and tape drives, is to store permanent information. The magnetic medium on which information is stored is called a volume. Tape drives and certain disk drives have removable volumes, so a drive may contain different volumes at different times. Many newer disk drives have fixed volumes that cannot be removed from the drive, though an entire StorageWorks drive can be swapped.

DCL applications often describe or manipulate devices, usually hardware components. For example, an application might display information about the disks on a system or mount a tape volume on a tape drive. This chapter describes methods for obtaining device information and manipulating devices in DCL.

19.1 Device Names

Each device on an OpenVMS system and each device within an OpenVMS Cluster configuration has a unique device name. The name is used to refer to the device in file specs and DCL commands that require a device name, such as MOUNT. In the early days of OpenVMS, the format...