I have an AIX filesystem at 100% and I need to increase it by 30gb. Please give me the command to do this. Thanks in advance.

I tried this command and got this error:

chfs -a size=+500M /dev/test1223
0516-404 allocp: This system cannot fulfill the allocation request.
There are not enough free partitions or not enough physical volumes
to keep strictness and satisfy allocation requests. The command
should be retried with different allocation characteristics.

What steps should I take to make this work, and I do mean detailed steps. Thanks.

It looks from that error that you havn't the space free on the disk to do that.
However, you could use smitty to grow it - it'll make a few guesses as to where to find the disk - might help.

I tried to change it in smitty under:
Change / Show Characteristics of a Journaled File System

and I get this error:

COMMAND STATUS

Command: failed stdout: yes stderr: no

Before command completion, additional instructions may appear below.

chfs: 0506-932 Can not extend a JFS file system with nbpi = 4096
and frag = 4096 past 134217728 (512 byte blocks).

Looks to me like you don't have the space in the right place on the disk to do that then