instance, database issues

[yls177]

Below is my understanding. Please correct if i am wrong.

1) Normally, there is only one instance in a database with its own set of oracle software. Its also possible to have several instances in the same database, thereby each has its own SID and own sets of datafiles.

2) Alternatively, we could have these instances residing in their own databases each having its own orale software.

I searched this forum and hit upon the below

http://www.dbasupport.com/forums/sho...tance+database


My question s

a) How can i identify which scenario i am in (1) or (2). I am interested in identifying whether my instances are residing in one database or separated in different databases?

b) Please correct me if i get the above wrong.

Thanks!

[davey23uk]

you need to understand the concepts of what an instance and a database are

An instance doesnt have any datafiles or software. An instance is just a collection of processes and memory structures.

An instance opens a database (which consists of files). An instance can only open one database. A database can be opened by many instances (RAC)