maxfiles (and maxfiles_lim) are runaway program fences. That is, they simply prevent bad programs from using all the open file descriptors. If you have programmers that insist on opening thousands of files at the same time in a single program, then you'll have to decide whether to let those programs run on your system (by increasing maxfiles and maxfile_lim) or asking them to rewrite their program(s).
maxfiles is a per-program limit for the maximum number of files that can be opened at one time. This is a soft limit which can be changed using the setrlimit system call or with the HP-UX POSIX shell using ulimit -n (man sh-posix). Once ulimit has been set in the shell (see ulimit -a) for file descriptors, all subsequent processes started from that shell will inherit the new value for maxfiles. ulimit defaults to a new hard limit. Use the -S option to change up or down.
maxfiles is best left at 60 to 100 as the default value (put it into /etc/profile and /etc/csh.login) and allow specific processes to run at a higher limit with a start script. maxfiles cannot be increased beyond the kernel's hard limit of maxfiles_lim.
NOTE: If you have a dozen processes that all need 5,000 files opened at the same time, then the kernel parameter nfile must be increased by 60,000 to accomodate all the open files. nfile is for every file descriptor, not just unique files.
Bill Hassell, sysadmin
