RAC means one single physical database can be installed on more than one physical computer or server for balancing workload and backup data?RAC stands for Real Application Clusters. It allows multiple nodes in a clustered system to mount and open a single database that resides on shared disk storage. When a single system fail (node), the database service will still be available on the remaining nodes.
if yes, what kind company needs this? employees more than 10000?It is not a matter of number of users as it is a matter of the availability of the database. If you cannot afford a single point of failure, then RAC should be taken into consideration.
can we also setup one single application on more than one computer? divide the application tier into components, and setup them on different computers?eg http on server A, form on server B, etcYes, and this is called "Multi-node Installation".
It would be interesting to have EBS RAC customers indicate how many unplanned outages they had in the past year due to RAC/CRS crashes...
can we setup both servers in working mode at same time for daily work?Have a look at this link: