I queried V$LIBRARYCACHE and found get_hit_ratio of namespace index is .035.
I guess indexes are reason of my db performance degradation.

I have already reindex all important transactional tables but get_hit_ratio of index remain around same ration.

I would like to know
whether simply reindexing is enough or thr is another better way to reindex?
How do i get know which index is being corrupted?