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Caused by: java.sql.BatchUpdateException: Lock wait timeout exceeded; try restarting transaction

// This function inside a Job implementation of Quartz Job
execute(...)
{
     UserTransaction trans = getTransaction();
     trans.begin();

     Session session = getSession();

     List<PersistedObject> list = getListOfPersistedObjects(...)

     int counter = 0;
     loop(l : list)
     {
           counter++;

          // this is just sending a message using information based on the object
           sendMessage(l); 

           // Create a 2nd \"archive\" object based on the data inside the l object
           PersistedObjectArchive archive = new PersistedObjectArchive(l)

           session.save(archive);
           session.flush();

           session.delete(l);
           session.flush();

           if(counter % JDBC_BATCH_SIZE_CONSTANT_FROM_SOMEWHERE == 0)
           {
                session.flush(); // Deadlock Exception happens here
                session.clear();
           }
     }

     trans.commit();
}