Re: Multiple Instances - when do you use them?

My 2 cts:
First of all : one instance manages one single database. A single database can be opened by multiple instances, but this applies to the parallel server situation ONLY. Parallel server usually applies, when you want to have very high availability, a database failing over, when one of the two (usually not more) instances crashes. It also applies when you have several groups of users which are performing completely different sort of actions on one database. Think of one group of users doing data entry work and a different group of users running batch jobs. A combination of the two on one server can be a disaster, while an OPS configuration can be very beneficial. Usually people are using multiple instances when they want multiple databases. You see this very often when people migrate from Sybase or Sql-Server to Oracle. In the Sybase world a database is more or less the same as a tablespace in Oracle. In Oracle you can implement this as multiple schemas in one database. You should only implement this is a multiple databases as the two applications are completely unrelated, they never interconnect, and you want complete separation (for security reasons) of the two user communities. Also in this case, there should be no or mimimal overlap between the two user communities. This is the more important because multiple instances on one server is usually a very bad thing performance wise.

Hth,

--
Sybrand Bakker, Oracle DBA
DRODRIGU1 <drodrigu1_at_aol.com> wrote in message news:19991203231445.25725.00000458_at_ng-fx1.aol.com...
> Could anyone tell me why would I need more than one instance on a
database?
> Is this to increase the number of users? Thanks.
>
> DR
Received on Sat Dec 04 1999 - 00:01:27 CST