PrintKit queues configured for TCP/IP communications do not have an associated device that can be used by software that expects to be able to write output to a queue using a virtual device. However, you can create such a virtual device for a PrintKit queue.
OpenVMS allows programs to send output to a print queue as though they were writing directly to an output device. To do this, it provides a “virtual” device interface that saves the data as it is written and, when it is complete, spools it for printing. There is a considerable body of legacy code that takes advantage of this capability. (In particular, this is how MUMPS programs do printing.)
For a queue that communicates with a printer over a dedicated link, there is a device associated with the queue that can be used for the virtual device interface (the device responsible for the physical connection, or a LAT device configured for a particular network service). However, for a PrintKit queue using TCP/IP communications, the associated device is the shared network interface, which cannot be used as a virtual device.
The simplest way to get around this limitation is to use a LAT device to provide the virtual device interface and configure it to spool its output to the PrintKit queue. In this arrangement, the LAT device serves only as a “placeholder.” It is never actually used for LAT communications – so its node and port settings do not matter, and it doesn't need to be connected to anything.
1.Create the LAT device to be used as the virtual device. Choose an unused device number that is consistent with your local policies for allocating LAT devices:
$ MCR LATCP
LATCP> CREATE PORT lat-device /APPLICATION
(Specify the actual lat device you've chosen.)
2.Set the LAT device to be spooled to your PrintKit queue:
$ SET DEVICE lat-device /SPOOLED=queue-name
(Specify the actual LAT device and PrintKit queue.)
3.These commands should be placed in your startup file so that the LAT device is recreated and configured when your system reboots (normally SYS$STARTUP:SYSTARTUP_VMS.COM).
1.Configure the LAT device LTA100: for spooling to the PrintKit queue PRINTKIT:
$ MCR LATCP
LATCP> CREATE PORT LTA100: /APPLICATION
$ SET DEVICE LTA100: /SPOOLED=PRINTKIT
The OpenVMS System Manager's Manual: Tuning, Monitoring and Complex Systems provides a discussion of LAT services.