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You've asked a question in which all of the details are not yet known.
The grid concept is new for Oracle and the first database version to
support grids does not yet support grids as fully as it should. Future
versions will expand on Oracle's capability to fully utilize grids.
The idea of grids started from the electrical utility companies. Your
house is receiving its electrical power from one of these companies.
There are many electrical power supply companies. And they have
redudancy built into their systems. Should a power substation go down,
you shouldn't be without power as other components of the electrical
grid will handle the load. Now in practice is doesn't always work this
way otherwise you'd never experience a power outage, but that's the
basic idea.
Computing has taken this grid concept in order to achieve two goals,
higher availability and the ability to add resources on demand. With a
grid, if a component of the grid goes down, you do not lose any
availability. Let's say you have five servers in your organization, two
database servers, two application servers, and an email server. If one
of the database servers goes down it would be nice if another one of
the five servers can run the database. Many people also buy servers for
a specific task. In our scenario, we have two database servers, each of
which has more than enough processing power for the databases. What if
we want to add another database? Do we buy another server? With grids,
you might not have to. Simply add the database to another server. If
there are not enough resources on that server, the grid will take
resources (CPU, memory) from a server which is not fully utilizing its
resources. In this case, a high demand on one of the database servers
might mean that the email server which isn't as busy can come to the
rescue with its underutilized resources. The grid concept is supposed
to let you use idle resources on all your servers in the grid to handle
all needs of all applications on the grid.
That's the dream anyway. The Oracle database isn't quite there yet.
What is in place is to use multiple servers to run your database.
Oracle's Real Application Clusters, which has been around before 10g,
lets you run the database on multiple servers. Need more resources to
satisfy that end of year processing? With 10g, you can simply plug
another server into the cluster. When end of year processing is
complete and you do not need that server, simply unplug it and use it
for something else. With this concept, companies should be able to
better use their hardware resources to support their constantly
shifting workloads. The heart of the grid computing effort with Oracle10g is the Real Application Clusters. I think it still has a way to go
to live up to all of its hype, but it is a good start.
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