Using RRD for Oracle Database Monitoring

Hi

I am figuring out to monitor the Oracle Database Various Metrics using
RRD tool.
i want to measure HitRatios for Oracle Database.
After reading the available material and tutorials on the WEB.
regarding rrdtool <create|update|graph>
I am totally confused.

Since as i mentioned i want to measure Database Hit Ratios for
Buffer
Dictonary
Library ( All the hitratios are in percentages %s)

when creating RRD database what DST(Data Source Type) i have to use
among
<Guage|Counter|Derive|Absolute> for the above scenario and why it is
help ful

I am Confused.............

Can any one throw some light and comments on my confusion.