Oracle Database 11g Oracle Real Application Clusters Handbook, 2nd Edition, 2nd Edition

Resources and Enqueues

A resource is an identifiable entity—that is, it has a name or reference. The referenced entity is usually a memory region, a disk file, a data block, or an abstract entity; the name of the resource is the resource. A resource can be owned or locked in various states, such as exclusive or shared. By definition, any shared resource is lockable. If it is not shared, no access conflict can occur. If it is shared, access conflicts must be resolved, typically with a lock. Although the terms lock and resource refer to separate objects, they are often used interchangeably. A global resource is visible and used throughout the cluster. A local resource is used by only one instance. It may still have locks to control access by the ...