we are having very low package cache hit ratio approx about 45%
earlier the self tuning was not enabled and i have allocated PCKCACHESZ 25000 4K pages . At that it used to be around 58% but making this parameter as automatic has reduced to hit ratio. On db2diag i can see sometimes PCKCACHESZ reaching 300000.
overflow never happens.
what should i change or monitor to have high Hit ratio

db2 9.1.3
win 2003