JDBC API 2.0 defines five levels of transaction isolation for database concurrency control. Which of the
following is the lowest level of transaction isolation?

A.
TRANSACTION_SERIALIZABLE

B.
TRANSACTION_NONE

C.
TRANSACTION_READ_COMMITTED

D.
TRANSACTION_READ_UNCOMMITTED

E.
TRANSACTION_REPEATABLE_READ

Explanation:
There are five levels of transaction isolation provided by JDBC 2.0 Connection interface. The higher the
transaction level, the more the care is taken to avoid database conflicts. On the other hand, the higher the level
of isolation, the slower the application executes (due to increased locking overhead and decreased
concurrency between users). The developer must balance the need for performance with the need for data
consistency when making a decision about what isolation level to use. However, the level that can actually be
supported depends on the
capabilities of the underlying DBMS.
The highest transaction isolation level specifies that if one transaction is operating on a database, no other
transaction can access that part
of the database.
The transaction isolation levels in terms of concurrency control in ascending order are as follows:
TRANSACTION_NONE
TRANSACTION_READ_COMMITTED
TRANSACTION_READ_UNCOMMITTED
TRANSACTION_REPEATABLE_READ
TRANSACTION_SERIALIZABLE
The lowest transaction isolation level, i.e. TRANSACTION_NONE, specifies that transactions are not at all
supported.
A developer can change a transaction isolation level by using the setTransactionIsolation() method of the
Connection interface.