Using JDBC Transaction Isolation Levels (Sun GlassFish Enterprise Server v2.1.1 Developer's Guide)

Sun GlassFish Enterprise Server v2.1.1 Developer's Guide

Using JDBC Transaction Isolation Levels

For general information about transactions, see Chapter 16, Using the Transaction Service and Chapter 12, Transactions, in Sun GlassFish Enterprise Server v2.1.1 Administration Guide. For information about last agent optimization, which can improve performance, see Transaction Scope.

Not all database vendors support all transaction isolation levels available in the JDBC API. The Enterprise Server permits specifying any isolation level your database supports. The following table defines transaction isolation levels.

Table 15–1 Transaction Isolation Levels


Transaction Isolation Level	Description
`TRANSACTION_READ_UNCOMMITTED`	Dirty reads, non-repeatable reads, and phantom reads can occur.
`TRANSACTION_READ_COMMITTED`	Dirty reads are prevented; non-repeatable reads and phantom reads can occur.
`TRANSACTION_REPEATABLE_READ`	Dirty reads and non-repeatable reads are prevented; phantom reads can occur.
`TRANSACTION_SERIALIZABLE`	Dirty reads, non-repeatable reads and phantom reads are prevented.

Note that you cannot call setTransactionIsolation() during a transaction.

You can set the default transaction isolation level for a JDBC connection pool. For details, see Creating a Connection Pool.

To verify that a level is supported by your database management system, test your database programmatically using the supportsTransactionIsolationLevel() method in java.sql.DatabaseMetaData, as shown in the following example:

InitialContext ctx = new InitialContext();
DataSource ds = (DataSource)
ctx.lookup("jdbc/MyBase");
Connection con = ds.getConnection();
DatabaseMetaData dbmd = con.getMetaData();
if (dbmd.supportsTransactionIsolationLevel(TRANSACTION_SERIALIZABLE)
{ Connection.setTransactionIsolation(TRANSACTION_SERIALIZABLE); }

For more information about these isolation levels and what they mean, see the JDBC API specification.

Note –

Applications that change the isolation level on a pooled connection programmatically risk polluting the pool, which can lead to errors.