Data Dict Hit Ratio

Gets - Total number of requests for information on the data object.

Cache Misses - Number of data requests resulting in cache misses

Hit Ratio should be > 90%, else increase SHARED_POOL_SIZE in init.ora

select sum(GETS),
sum(GETMISSES),
round((1 - (sum(GETMISSES) / sum(GETS))) * 100,2)
from v$rowcache