HP-UX Socket Connection Limit
By admin on Feb 3, 2009 in side note
System wide limited by “tcp_conn_request_max”
# ndd -get tcp_conn_request_max
…to show the value
# ndd -h tcp_conn_request_max
…to show the ranges allowed
# ndd -set tcp_conn_request_max >value>
…to set the value
Limit by maxfiles per process. ulimit -n is a soft limit set by the kernel parameter maxfiles. You may change this with the standard HP-UX POSIX shell with ulimit:
#ulimit -Sn 500
It is recommended to use -S to set a soft limit which will allow ulimit to increase the value in the current environment. Without -S, ulimit makes the value a hard limit which can only be changed downward at a later time. ulimit is a shell builtin and it can be used in a shell script to set the limit for processes run from the script.
The second limit is maxfiles_lim which is the system-wide limit for maxfiles. ulimit (or the program library call setrlimit) can’t set the file descriptor limit higher than maxfiles_lim. It is good system practice to limit maxfiles to a low value if you have developers that might create a runaway program, and use ulimit only when necessary.
The last limit is nfile, the kernel parameter for all open files. maxfiles exists to help avoid exceeding nfile. If you have a program that needs to open 500 socket connections and the program will be run 10 times, nfile will have to be increased by 5000 to accomodate all the sockets.
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