Oracle Database Discussions

Hello All,

I have below list of question/confirmation required:

1. Is it possible to install two database servers on single physical box?
2. When we create one more database using DBCA then is it that we are creating one more SID?
3. Having 2 SID is nothing but having 2 instances on your database server? This means that if you want to run 2 instances of a db server then ought to have 2 SID's?
4. A schema can only be created under an SID and whenever we are creating a schema we are essentially creating one more user because username and schema name must be same.
5. Each SID can have multiple schema under it.

My basic doubt is between SIDs and multiple instances of db server.
Highly appreciate if somebody can reply for all 5 point and throw clear differentiating light on SIDs and multiple instances of db server.

Regards,
Himanshu