ds server

hi
I just installed toad on my system and in the server analysis part i get the following:

Buffer cache hit ratio : 48.2746 may need to increase db_block_buffers

library cache get hit ratio : 83.0791 dynamic or unsharable SQL

library cache pin hit ratio : 83.7397 shared pool area too small

redo space wait ratio : 4.0190 unknown

chaned fetch ratio 0.0981 pctfree too low for a table

parse to execute ratio 75.4294 high parse to execute ratio

DBWR average scan depth 1.430.6494 no of db_files too high?

what does all thse mean...are all thse some kinda errors on the server
if yes..is there anyway to get 'bout this.....?

thanx