Oracle Database Discussions

Hi

I am new to Oracle server architecture.
Please correct me if am wrong.

As per my understanding, the data that we retrieve from a SQL query is stored in SGA in Database buffer cache.

I have some queries:

1. Does the database buffer cache store only data from SQL queries or anything else also? What is its size? Can we set the size?
2. Where are the parsed SQL queries stored - SGA or PGA? And where exactly? I want to know if all the users connected in an Instance have access to each other's parsed SQL queries?
3. SGA is shared by all users in an Oracle Instance? PGA and UGA are local to a specific user in an instance? Is it correct?


Thanks
Abhi