Oracle resolves issues by using various types of locks and a multiversion consistency model. These features are based on the concept of a
transaction
The simplest way to think of Oracle's implementation of read consistency is to imagine each user operating a private copy of the database, hence
the multiversion consisten-
cy model
Oracle also uses locks to control concurrent access to data. When updating information, the data server holds that information with a lock until the update is
submitted or committed
One way to provide from concurrent non-database administrator isolation is to shut down the database and reopen it in restricted mode. You could also put the system into quiesced state without disrupting users
RAC comprises several Oracle instances running on multiple clustered computers, which communicate with each other by means of a so-called interconnect
Oracle provides unique portability across all major platforms and ensures that your applications run without modification after changing platforms