Kodo changes commit order in multithreaded scenario,resulting in DBdeadlock

Question

We are currently using KODO version 3.4.1 as indicated by kodo-jdo-runtime-3.4.1.jar and kodo-jdo-3.4.1.jar. This is what is currently happening to our application in a scenario where multiple threads are trying to access the same set of tables. It results in a Oracle DB deadlock for one of the threads transactions. If kodo commits all the DB transactions in the same order as we had set in a particular transaction for each thread,then this deadlock wont occur, but what I noticed is that KODO changes the order in which the commit happens on the tables. Any help will be appreciated.

Answer 1

I have a simple example below which will illustrate actually what is happening which is resulting in a Oracle DB deadlock.
There are more that 4-5 tables that are being updated before a commit can happen.
Consider the following scenario
kodoPersistenceManager.makePersistent(table 1);
kodoPersistenceManager.makePersistent(table 2);
kodoPersistenceManager.makePersistent(table 3);
kodoPersistenceManager.makePersistent(table 4);
kodoPersistenceManager.makePersistent(table 5);
persistenceManager.close();
where persistenceManager is an instance of KodoPersistenceManager and
kodoPersistenceManager is also an instance of KodoPersistenceManager.
When multiple threads are trying to do the same operation which involves the same 6 statements as above being called, based on SQL trace thrown out by kodo I realised that kodo changes the commit order to something as shown below.
kodoPersistenceManager.makePersistent(table 2);
kodoPersistenceManager.makePersistent(table 3);
kodoPersistenceManager.makePersistent(table 1);
kodoPersistenceManager.makePersistent(table 4);
kodoPersistenceManager.makePersistent(table 5);
persistenceManager.close();
This results in a DB deadlock in the oracle database which rolls back the above transaction. There is a dependency that tables must be persisted in order table 1,table 2,table 3,table 4,table 5,table 6.
Any idea how this can be avoided? Thanks in advanvce