Re: Study Q1: One Database Can Have Multiple Instances?

In article <8peqt3$cgl3d$1_at_ID-41926.news.cis.dfn.de>,   "Dino Hsu" <dino1_at_ms1.hinet.net> wrote:
> Dear All,
>
> The document mentions one database can have multiple instances
 (parallel
> server), but I have no experience of this setting, I wonder:
> 1.Why does one database need multiple instances at the same time?
> 2.Will it make the implementaion very complicated?
> 3.Is parallel server specific to Unix and doesn't work for Windows
 NT/2K?
> 4.Can you show me an implementation example, if it is useful?
>
> Thanks in advance.
> Dino
>

Oracle Parallel Server, OPS, is used in high availability environments and involves multiple instances, each on a separate machine, accessing a shared (hopefully redundant) disk array.

If machine A fails the database is still available through machine B. There are various means of automatic fail-over and load balancing available depending on the hardware/software/application.

It is now possible for these two machines to be far, far apart, perhaps even around the world from each other.

When data is selected on instance A on machine A it contacts instance B on machine B to see if the target data has been updated but not yet written. If not then no problem, if it was the changed then the changed data passed. This is an over simplification, but if you want to know more you can read the OPS Manual on the documentation CD.

--
Mark D. Powell  -- The only advice that counts is the advice that
 you follow so follow your own advice --


Sent via Deja.com http://www.deja.com/
Before you buy.