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 allocated dynamically.
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 away.
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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I was taught that the human brain was the crowning glory of evolution so far, but I think it’s a very poor scheme for survival (Kurt Vonnegut).