SQL Cache Hit Ratio

Pins - The number of times a pin was requested for objects of this namespace.

Reloads - Any pin of an object that is not the first pin performed since the object handle was created, and which requires loading the object from disk.

Hit Ratio should be > 85%

select sum(PINS) Pins,
sum(RELOADS) Reloads,
round((sum(PINS) - sum(RELOADS)) / sum(PINS) * 100,2) Hit_Ratio
from v$librarycache