How to display and modify the AIX system parameters

This is very important, since most of the users I work with are programmers and bump into the default upper limits that are assigned to all users by the system.

Setting these parameters allow them to overcome temporary problems, such as the number of files opened for instance.

Command 'ulimit' and its default parameters

This is a straight copy of the AIX man page:

The ulimit command sets or reports user process resource limits, as defined in the /etc/security/limits file. This file contains these default limits:

fsize = 2097151
core = 2097151
cpu = -1
data = 262144
rss = 65536
stack = 65536
nofiles = 2000 

Here is another example :

$ ulimit -a
time(seconds)        unlimited
file(blocks)         unlimited
data(kbytes)         131072
stack(kbytes)        32768
memory(kbytes)       32768
coredump(blocks)     2097151
nofiles(descriptors) 2000

The lsattr command

At any time, the maxuproc (max. number of processes per user) can be obtained with the following command:

lsattr -E -l sys0 -a maxuproc 

The lsattr -D displays the default values for all users:

bash-3.00# lsattr -Dl sys0 -a maxuproc
maxuproc 128 Maximum number of PROCESSES allowed per user True

Finally, the command chdev allows you to modify the value of maxuproc and other system parameters. See the following web site for more examples.

Modifying system parameters through smitty

Another way to modify system parameters is to go through smitty the swiss army knife AIX configuration tool.

I don't like smitty, but it has its uses. Here is how to do it: launch smitty, go to system environments and next to change/show characteristics of the operating system. You will find there a complete list of system parameters, along with their values.

The commands chdev and chuser can also be used instead of smitty. Use the F6 function key, while in smitty to display the command as it is going to be executed.

See Also