Why double-spool print jobs?

[Chris Lewis]

In article <28996 at uflorida.cis.ufl.EDU> ruck at reef.cis.ufl.edu (John Ruckstuhl) writes:
|We have commercial electronics design software, Valid, running on Suns.
|This SW insists on double-spooling plotter jobs.  
|    Does this make sense?
|    Is this a common solution among SW products?
|I don't see the necessity or advantage.

|From the Valid Guide to Operations explanation:

|    The double spooling allows other programs to access plotters in an
|    orderly fashion, and keeps (application) users from having to wait
|    for their plots to be processed.

|Can't one achieve the same effect, and wouldn't it be cleaner, if the SW 
|just sent the data directly through the application-filter to the print 
|spool in the background.

The reason for this is simple - presumably the application filter is
kinda slow and a bit of a hog, so the double spooling prevents more than
one simultaneous execution of the application filter.  Which is the polite
thing to do if more than one simultaneous invocations causes your machine
to crawl.
-- 
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