[sadiq31279]

I am confused with the term DB & Instance. Is it 2 different terms if yes then how does it differs.

have a nice day.

[Orca777]

right,
the db is the physical database with it's datafiles, logfiles, controlfiles.
the instance is allocated memory in shared memory with its' defined backendprocesses like pmon, smon, arch, logwr dbwr, chkpt ...
and the user processes.
so you do not start a db you start the instance.
one db could have two instances -> parallel server/Real Application cluster.

Orca

[clio_usa]

Think about as many people using the same computer in the same time.

The computer is the database files, the people are the db instances.

Each instance has its own SGA and processes, attaching to the same set of data (datafiles). Each instance however could have it's own control files.


Hope that helps,

clio_usa
OCP - DBA