GT.M OPEN, USE, and CLOSE commands have an argument expression specifying a device name. In the OpenVMS environment, a device may be referred to either by its physical name or by a logical name to which its physical name has been assigned.Because logical names permit program coding independent of hardware configuration, logical names are more common than physical names.

During an OPEN, GT.M attempts to resolve the specified device names to physical names. When GT.M successfully resolves a device name to a physical device, that device becomes the target of the OPEN. When the device name does not resolve to a physical device, GT.M attempts logical name translation; the result becomes the name of an RMS sequential disk file. The TMPMBX and PRMMBX deviceparameters on an OPEN command override the default mechanism, and specify that the device is a VMS mailbox.

Once a device is OPEN, GT.M establishes an internal correspondence between a name and the device or file. Therefore, while the device is OPEN, changing the translation of a logical name in the device specification does not change the device.

The following names identify the original $IO for the process: