A user process allows mvBase to communicate with peripheral devices; in most cases, such devices are user terminals. A user process can also manage any serial communications device such as a printer or a modem.
In the mvBase environment, fixed disk drives, backup tape drives, floppy diskette drives (which mvBase uses as tape drives), and parallel printers are not associated with any user process. The operating environment maintains internal Windows host operating system-dependent structures to manage activity on these devices.
With the exception of character terminals (which include physical terminals, Telnet sessions, networked mvTerm sessions and terminal emulators), peripheral devices are shared by all users. For instance, while each user has a terminal, there might be only one printer or backup tape drive configured in the mvBase environment. Since these devices can handle only one job at a time, the user needs to wait until he or she can get exclusive control of the device.
The Spooler is a special kind of process, called a phantom process, that is not associated with a communications line. The Spooler holds all users’ print requests and acts on them as a printer becomes available.
The Spooler monitors all printers so that users do not have to wait until the printer is available. Each user account is assigned a form queue that is serviced by one or more printers. The form queue assignment indicates specific printers that receive print jobs generated from that account. By changing the form queue assignment, the user can designate a specific printer or a printer loaded with a preprinted form. The user does not have to wait until the printer form queue becomes available to process a print job. A print job can be sent at any time, although the user may not see his job on the printer immediately if other print requests are ahead of it. Regardless, the TCL prompt returns to allow the user to continue working.
In the mvBase environment, a user process must attach a tape drive before reading or writing the tape, which gives the user process exclusive control of the device while other users are restricted from using the same tape drive.
Tape drives are referred to by a number representing a logical tape unit. Logical tape unit 0 is automatically selected for each user process. If other tape drives are available, the user must select the tape drive before it can be attached. When the user is finished using the tape drive, he detaches the drive. If the user logs off while attached to a device, the device is automatically detached and becomes available across the system.
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