Why can't I change the transaction isolation level?

Question

I was trying to change the transaction isolation level from an EJB. My source codes are shown as the follows:
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/*********************** Database Routines *************************/
private void makeConnection() {
try {
InitialContext ic = new InitialContext();
DataSource ds = ( DataSource )ic.lookup( dbName );
con = ds.getConnection();
DatabaseMetaData dmd = con.getMetaData();
show_supported_trans_levels( dmd );
int status = con.getTransactionIsolation();
System.out.print( "1. " );
disp_tx_status( status );
System.out.println( "con.isReadOnly() = " + con.isReadOnly() );
con.setTransactionIsolation( Connection.TRANSACTION_SERIALIZABLE );
System.out.print( "2. " );
disp_tx_status( status );
} catch( SQLException ex ) {
System.err.println( "SQLException: " + ex.toString() );
throw new EJBException("Unable to connect to database. " +
ex.getMessage());
} catch( NamingException ex ) {
System.err.println( "NamingException: " + ex.toString() );
throw new EJBException("Unable to connect to database. " +
ex.getMessage());
private void disp_tx_status( int status )
System.out.print( "Transaction Status: " );
switch( status )
case( Connection.TRANSACTION_READ_UNCOMMITTED ):
System.out.println( "TRANSACTION_READ_UNCOMMITTED" );
break;
case( Connection.TRANSACTION_READ_COMMITTED ):
System.out.println( "TRANSACTION_READ_COMMITTED" );
break;
case( Connection.TRANSACTION_REPEATABLE_READ ):
System.out.println( "TRANSACTION_REPEATABLE_READ" );
break;
case( Connection.TRANSACTION_SERIALIZABLE ):
System.out.println( "TRANSACTION_SERIALIZABLE" );
break;
case( Connection.TRANSACTION_NONE ):
System.out.println( "TRANSACTION_NONE" );
break;
default:
System.out.println( "UNKNOWN" );
break;
private void show_supported_trans_levels( DatabaseMetaData dmd ) throws SQLException
System.out.println( "List of Supported Transaction Isolation Levels: " );
if( dmd.supportsTransactionIsolationLevel( Connection.TRANSACTION_READ_UNCOMMITTED ) )
System.out.println( "TRANSACTION_READ_UNCOMMITTED is supported!" );
else
System.out.println( "TRANSACTION_READ_UNCOMMITTED is unsupported!" );
if( dmd.supportsTransactionIsolationLevel( Connection.TRANSACTION_READ_COMMITTED ) )
System.out.println( "TRANSACTION_READ_COMMITTED is supported!" );
else
System.out.println( "TRANSACTION_READ_COMMITTED is unsupported!" );
if( dmd.supportsTransactionIsolationLevel( Connection.TRANSACTION_REPEATABLE_READ ) )
System.out.println( "TRANSACTION_REPEATABLE_READ is supported!" );
else
System.out.println( "TRANSACTION_REPEATABLE_READ is unsupported!" );
if( dmd.supportsTransactionIsolationLevel( Connection.TRANSACTION_SERIALIZABLE ) )
System.out.println( "TRANSACTION_SERIALIZABLE is supported!" );
else
System.out.println( "TRANSACTION_SERIALIZABLE is unsupported!" );
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However, I encountered the following exception when running at the highlighted statement:
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SQLException: java.sql.SQLException: Transaction manager errors. statement not allowed in XA Session.
======================================================
To my surprise, the isolation level TRANSACTION_SERIALIZABLE is supported from the database vendor. So why can't I change the transaction isolation level?

Answer 1

You can change the setting, you may need to click the lock at the bottom of the preference pane. Be careful what you download and install, Gatekeeper is there to help you. OS X: About Gatekeeper - Apple Support