You do not say it is AIX, but /etc/security/(limits) is probably AIX.
Correct the value you want for a "limit" and use the followiung command to change one or more of several values
chuser fsize=-1 cpu=-1 data=-1 stack=-1 core=-1 rss=-1 root
Consider the following (fsize value is 512-byte blocks)
michael@x071:[/home/michael]dc
1024 1024 1024 * * p
1073741824
512 / p
2097152
2 * p
4194304
To adjust the classic ulimit way, just enter:
ulimit -f 4194304
To make it permanent (starting with next login) use:
chuser -a fsize=4194304 root
and you have the max ulimit filesize to 2Gbyte (4194304 * 512)