hitrate ratios

[itwizzkid]

I have free shared_pool_size of 67MB but my dictionary cache hit rate is showing this

select (1-(sum(getmisses)/sum(gets))) * 100 "Hit Ratio" from v$rowcache
Hit Ratio
----------
22.6712589

What affect is this having on database performance and how do I increase this to an acceptable level?

Thanks

[Sameer]

Well, the acceptable hit ratio should be atleast 85%+. You will not directly able to tune dictionary cache, you need to tune your shared_pool (library cache). Do not analyze rowcache hit ratio immediately after starting instance, because none of the objects are cache at that time, so the rowcache hit ratio will be bad. There are many areas wherein you can look into and increase dict cache hit ratio... F.ex If you are using sequences, then see to it that you cache sequence entries, Even if you select one value from sequence, it will change val of dc_sequences in v$rowcache, then avoid dynamic extent allocation etc...


For more deails refer to ..

http://download-west.oracle.com/docs...mory.htm#53186


Sameer