AIX

Paging space is 100% full? what step can i take

if you can login to the system, or you are sill logged in, but can't issue any commands because of the lack of memory, you could try to

Code:

cd /proc
echo *

and issue kill -9 on some of the higher process ids
but then reboot the system to have a clean start

To avoid this in the future, you might want to check, which application is filling your paging space. You could write some script using svmon for example to check out which processes are using paging space. There is an column that shows which process is using how much paging space - that one you will have to monitor (write a script, put it into crontab).
Paging activity itself is slowing down a system usually quite hard and should be avoided. When paging space is full, you have already the worst case.

Also consider if your system might need some performance tuning in terms of memory. If even this won't help and if you can't find any memory leaking process, you might want to consider to get more RAM.

forgot the possibility to add memory, as zaxxon wrote, what, of course is possible with dlpar online dynamically
but that usually wont work if your system is already at 100% paging space