Unix, Xenix and ODT General FAQ
This article is from a FAQ concerning SCO operating
systems. While some of the information may be applicable to any OS,
or any Unix or Linux OS, it may be specific to SCO Xenix, Open
This is an old article about SCO Unix and is only left here for historical purposes.
There is lots of Linux, Mac OS X and general Unix info elsewhere on
this site: Search this site is the best
way to find anything.
This is usually one of two things. There is a tunable kernel
parameter, NPROC, which determines the maximum number of
processes that may be running at any time. You may have exceeded
this limit. The usual method of solving this is to increase it a
fair bit and see if the problem goes away. If you are running on
OSR5, this is unlikely to be the reason, as NPROC is
There is another tunable kernel parameter, MAXUPRC, which
determines the maximum number of processes any one user may have
running at one time. Under Unix, for example, a large number of
mail messages being processed at once may cause this to be exceeded
by MMDF, usually resulting in "uux failure - pipe broke" or similar
messages. Once again, increase it and see if the problem goes
Also, have a look at the console and/or /usr/adm/messages
for any system messages which appeared at the same time the user
got this message. They may point to another potential reason, such
as being out of swap space or exceeding NREGION. See Why did my region table overflow?).
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