Oracle, Serializable and java.sql.SQLException

Question

I'm reading in the weblogic documentation about serializable transactions
and Oracle at:
http://www.weblogic.com/docs51/classdocs/API_ejb/EJB_environment.html
I've excerpted below the section of interest. Essentially it says that if
you want to use an isolation level of SERIALIZABLE with Oracle,
you must be prepared to catch and retry transactions which fail due
to the "can't serialize access for this transaction". What I don't understand,
is where do I catch this exception. The doc below suggests that it
is in the EJB client code. By this, I assume it should be caught
by any client calling into an EJB method which is starting a transaction.
What I don't understand is I didn't think that ejb methods threw a
java.sql.SQLException. How can I catch this exception? The
exception is caused at commit time, which I don't have any
direct control over since I am using CMP.
Do I then need to inspect the exception text for the string:
"ORA-08177: can't serialize access for this transaction", in order
to determine whether to retry the transaction?
Is there any sample code for this. I just need to know where
the exception should be caught in my code, and how to
inspect the exception (scanning text based error messages
sounds problematic, since the exact message text might
change over versions of the database and deployment, etc.).
I am planning on using CMP, so I am not making any
jdbc calls directly.
Jason
Special note for Oracle Databases
Keep in mind that Oracle uses optimistic concurrency. As a consequence, even with a setting of TRANSACTION_SERIALIZABLE, Oracle does
not detect serialization problems until commit time. The message returned is:
java.sql.SQLException: ORA-08177: can't serialize access for this transaction
Even if you use the TRANSACTION_SERIALIZABLE setting for an EJB, you may receive exceptions or rollbacks in the EJB client if
contention occurs between clients for the same rows. To avoid these problems, you must ensure that clients catch and examine the SQL
exceptions, and take appropriate action, such as restarting the transaction.
Jason Rosenberg
SquareTrade
(remove 'nospam' from my return address)

Answer 1

I'm reading in the weblogic documentation about serializable transactions
and Oracle at:
http://www.weblogic.com/docs51/classdocs/API_ejb/EJB_environment.html
I've excerpted below the section of interest. Essentially it says that if
you want to use an isolation level of SERIALIZABLE with Oracle,
you must be prepared to catch and retry transactions which fail due
to the "can't serialize access for this transaction". What I don't understand,
is where do I catch this exception. The doc below suggests that it
is in the EJB client code. By this, I assume it should be caught
by any client calling into an EJB method which is starting a transaction.
What I don't understand is I didn't think that ejb methods threw a
java.sql.SQLException. How can I catch this exception? The
exception is caused at commit time, which I don't have any
direct control over since I am using CMP.
Do I then need to inspect the exception text for the string:
"ORA-08177: can't serialize access for this transaction", in order
to determine whether to retry the transaction?
Is there any sample code for this. I just need to know where
the exception should be caught in my code, and how to
inspect the exception (scanning text based error messages
sounds problematic, since the exact message text might
change over versions of the database and deployment, etc.).
I am planning on using CMP, so I am not making any
jdbc calls directly.
Jason
Special note for Oracle Databases
Keep in mind that Oracle uses optimistic concurrency. As a consequence, even with a setting of TRANSACTION_SERIALIZABLE, Oracle does
not detect serialization problems until commit time. The message returned is:
java.sql.SQLException: ORA-08177: can't serialize access for this transaction
Even if you use the TRANSACTION_SERIALIZABLE setting for an EJB, you may receive exceptions or rollbacks in the EJB client if
contention occurs between clients for the same rows. To avoid these problems, you must ensure that clients catch and examine the SQL
exceptions, and take appropriate action, such as restarting the transaction.
Jason Rosenberg
SquareTrade
(remove 'nospam' from my return address)