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As for the idea of grids, it derived from 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, it 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 e-mail server. If one of the database servers goes down it would be nice if another one of the five servers could run the database.
The Oracle database isn't quite there yet. What it does offer is the ability to use multiple servers to run your database. Oracle's Real Application Clusters (RAC), 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
Prior to Oracle9i, if you wanted to cluster multiple database instances together to access the same data, you would use a product called Oracle Parellel Server (OPS). Late in Oracle8i, the concept of Cache Fusion was introduced for OPS. Cache Fusion lets Oracle instances in the cluster send data back and forth to other instances without having to write the data to disk first. Having to write data to disk first was known as "disk pinging" and slowed down application performance. When Oracle9i was introduced, Oracle Corp renamed OPS to Real Application Clusters (RAC). This was due, in part, to Cache Fusion along with other improvements to the cluster software. Oracle10g still uses RAC in their documentation. But Oracle10g's grid strategy relies heavily on RAC for its implementation. Oracle is not calling the software "grid." At this time, grid is more of a concept that uses Oracle software for its implementation.
Automatic Storage Management (ASM) is one of the 'cool new features' in Oracle10g that is meant to reduce the workload for Oracle DBAs. ASM completely automates the process of creating logical volumes, file systems and filenames, with the DBA only specifying the location of raw disks and ASM doing the rest. Disk I/O is managed by evenly distributing the data across blocks within a disk group, with ASM in addition handling disk mirroring and the creation of mirror groups and failure groups.
ASM deals with the problems caused by rapidly expanding data warehouses, where administators can no longer deal with the sheer number of disk units, nodes and logical groupings, and is a key feature of the Oracle10g grid architecture, which aims to 'virtualize' computing power and present database features like processing and storage as utilities that effectively manage themselves.
In order to use Grid Control, you should first install OEM Grid Control (found on a separate CD) and configure it and its agents. Then, when installing Database 10g, the agent will be detected and you should be offered the option to manage this database as part of your grid.
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