Instances

[Noemi]

I would like to know what is better , have 2 instances or only one , and why ?

[mrvajrala]

What are your requirements ????

[thanigai]

I feel having 2 instances is better than one.
Thanigaivasan

[pravin]

is it having 2 instances in one Machine.
or what else.

Please put the question clearly, so that we can advise u , instead of putting a single liner question which doesnot mention what o/s and what application will be run.

--PRAVIN

[SANJAY_G]

A database can be mounted by one instance only unless you are using OPS.

Sanjay

[Tarry]

Depending on yr rqmts having 2 instances on the seperate server provides scalability.(allowing more connections and more transactions).
So one instance ats as a primary instance and the other as a failover instance.The failure/secondary instance takes over when primary fails.
This setup protects against instance failures etc but not against media/or non media failures.So don't think of it as an option for high availability against data failures* but scalability.
* here you might considering a stby database setup.

Hope that explains.
Tarry