What is a cluster in oracle? I tried finding the easy and clear information but did not find much on it..can anybody help?
asked
What is a cluster?
Consider two physical servers which both connect to shared storage.
You install oracle on both machines. Then you create the database on the shared disk. That's where all the actual data is stored.
You start a database instance on both machines. An instance is a set of processes and memory. Both those instances can open and work with the database on the shared disk. There's a whole bunch of software involved in making sure that if instance 'A' has read a data block from disk and made changes to it, and instance 'B' wants to make changes to the same block, they co-ordinate who has 'ownership' of the block.
A starting point for the official Oracle view is here
