I'm really confuse with the term instance and database. So, my first question is how database and Instance are related in Oracle, I mean, whether an instance is associated with one/multiple database(s) or a database associated with single/multiple instance(s)?
And, my second question is, one of my friend says we can't have multiple instances in oracle. is it really valid a statement ?
Best Answer
The documentation explains it very well:
An oracle database is the physical files that make up the database itself (control files, data files etc) - Documentation link.
A database is associated with one or more instances, with multiple instances making a RAC setup - Documentation link. As far as your second question is concerned, multiple instances of a single database is a RAC setup.