Serialization
The goal of a complete concurrency solution is to provide the highest level of isolation
between the actions of different users accessing the same data. As defined by the
SQL92 standard, this highest level is called serializable. As the name implies, serializable
transactions appear as though they have been executed in a series of distinct,
ordered transactions. When one transaction begins, it is isolated from any changes
that occur to its data from subsequent transactions.
To the user, a serializable transaction looks as though it has the exclusive use of the
database for the duration of the transaction. Serializable transactions are predictable
and reproducible, the two cardinal virtues of data integrity.
Of course, it??™s not trivial to have a database server support thousands of users while
each one thinks he is the only one. But Oracle manages to pull off this quietly dramatic
feat.
Oracle and Concurrent User Access
Oracle solves the problems created by concurrent access through a technology called
multiversion read consistency, sometimes referred to as MVRC.
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