FREELIM
FREELIM is a system parameter that sets the minimum number of pages that must be on the free-page list.
The system writes pages from the modified-page list, swaps out working sets, or reduces the size of the working sets to maintain the minimum count.
While the larger free-page list generally means less page I/O, it also means less space for the balance set, which tends to result in more swap I/O. You can monitor the size of the free-page list, the amount of page, and the amount of swap with the MONITOR IO command of the Monitor utility.