Multiple transactions

Question

Hey ppl,
I have a major problem with transactions. Im doing a DBMS with my application connecting to MS Access2000.
The problem ive got is that i cant execute more than one transaction. For example, if my gui has 2 buttons, and both execute a transcation each when pressed. If the first button is pressed, the appropriate transaction is executed properly. However, if i then press the second button straight after, its transaction is rolled back. im using the transaction isolation level TRANSACTION_READ_COMMITTED. Ive enabled and disabled auto commit mode appropriately and called the rollback methods. I just cant figure out whats going wrong.
PLZ COULD SUM1 GIV ME SOME SUGGESSTIONS!!! PLZ!!!!! ITS URGENT!!! THANKS!!!!

Answer 1

You start each transaction in its own connection,
don't you?
What's irritating me is, that you mean with
"Ive enabled and disabled auto commit mode
appropriately and called the rollback methods."
To do a transaction inside a connection, you must set
AutoCommit to false only once.
When do you rollback the transaction, and what shall
this help, after a locking conflict has happened?
What I can tell you about the reason - without seeing
any piece of code:
In isolation level TRANSACTION_READ_COMMITTED you get
a conflict if the first transaction has changed a row
and the second transaction tries to read it, before
the first transaction has committed it.Hey hartmut thanks for the reply. Here's some code which i thought might help clarify my problem.
The following code fragment is in a button listener:
try{
connect.setAutoCommit(false);
stmt.executeUpdate("insert into EMPLOYEES values (('"+forenameField.getText()+"'), ('"+surnameField.getText()+"'), ('"+add1Field.getText()+"'), ('"+add2Field.getText()+"'), ('"+cityField.getText()+"'), ('"+pcodeField.getText()+"'), ('"+telephoneField.getText()+"'), ('"+emailField.getText()+"'), ('"+usernameField.getText()+"'), ('"+passwordField.getText()+"'))");
stmt.executeUpdate("insert into WORK values (('"+usernameField.getText()+"'), 'None', 0, 0, 'Level 0', 'Day Off', 'Day Off', 'Day Off', 'Day Off', 'Day Off', 'Day Off', 'Day Off')");
stmt.executeUpdate("insert into HOURS values (('"+usernameField.getText()+"'), 0)");
connect.commit();
connect.setAutoCommit(true);
catch(SQLException sql){
try{
connect.rollback();
}catch(SQLException sqle){}
And the following fragment is in the listener for a different button:
try{
connect.setAutoCommit(false);
stmt.executeUpdate("delete from EMPLOYEES where USERNAME = ('"+usernameField.getText()+"')");
stmt.executeUpdate("delete from WORK where USERNAME = ('"+usernameField.getText()+"')");
stmt.executeUpdate("delete from HOURS where USERNAME = ('"+usernameField.getText()+"')");
connect.commit();
connect.setAutoCommit(true);
catch(SQLException sql){
try{
connect.rollback();
}catch(SQLException sqlex){}
I hope you might be able to see whats going wrong.
Sorry for the code not being too clear.
Thanks in advance.