John Korb ([log in to unmask]) wrote:
: Barry:

: The behavior you mentioned has been a part of MPE since at least 1978 and
: MPE II (which is as far back as I go on the HP3000).  If there are two or
: more printers in the same device class, the spool file at the head of the
: queue for that class goes to the first free printer in the class.  The
: situation gets a little more complex when you have printers which "share"
: queues.

Exactly (or almost exactly).  If multiple printers in the same device class
are available to print a file directed to that class when that file becomes
ready to print, the actual printer used can be pseudo-random.  The reason
is that "file ready" messages are sent to the spoolers for all of the
printers.  Whichever process is dispatched first grabs the file, the rest
find no file to print and go back to sleep.

I think Barry's question had to do with why print requests do not generate
REPLY requests as tapes do.  Tapes (and terminals) are the only devices
that generate REPLY requests -- it's been that way since the beginning.
Printers do not.

[...]

: When you have this many queues the interactions can become complex and
: determining which file will print next is sometimes difficult.  The rule
: appears to be (going out to the end of a limb) that if there is a file to
: print in one of the queues associated with a device that services
: multiple queues, the oldest spoolfile is printed first.

Your limb is sound :-).  When multiple files are available for a device,
the file chosen is the highest priority file above the systemwide (or
device-specific) outfence.  If there are multiple files at that priority,
the file which first entered the READY state (that is, was FCLOSEd by the
user) is selected.

-Larry "MPE/iX Spoolers 'R' Us" Byler-