Sorry, but I do not agree with such large Paging Spaces at all.
You don't want your application to use Paging Space since it will be really slow and will decrease the performance of your application considerably up to uselessness.

The old factors to size Paging Space do not fit anymore today at all.
For now 6 GB should be ok - you need to find out why your box is paging at all. There is some things you can tune on the behaviour how the Virtual Memory Manager (VMM) behaves when checking for the rate of RAM being used for file caching and for process data.
The other problem you could be, that you have a memory leak somewhere and that could be the reason you are running out of RAM and so it starts paging after some time.

For a start, please post the output of the following commands and use [code] and [/code] tags when doing so:

Code:

oslevel -s
vmstat -vs
vmo -x| grep -iE "minperm|maxperm|lru_file|poll"
svmon -G

## Have no AIX 5.3 at hand - I hope the syntax is still the same
svmon -P | awk '/Pid C/ {h=$0; next} NF == 9 && /^[0-9]/ {if($5 != 0) l[c++]=$0} END{print h; for(x=0; x<c; x++){print l[x]} }'