DCN Notification stops working after 10 to 12 hour in test environment

Question

Hi
We are using Oracle 11G and Java 5 (ojdbc5.jar).
We are using Oracle database change notification (DatabaseChangeRegistration) in java code to refresh the table cache (records of tables are stored in java hashtable for caching) in app server. The same code is working fine in production and was working fine in the test environment.
But from past one month we are facing issues in with our four application servers stop receiving the notification at the same time from the database, and we need to restart all the four application servers at the same time.
We are trying to find out if this issue is happening due to oracle database of some thing getting wrong with the java DatabaseChangeRegistration thread.
One more scenario is noticed if we are not restarting the app servers for almost one hour then this functionality start working again automatically, but some time it took more than hour too to get working without restart of the app servers.
We are using following code to register the Database change notification,
Properties prop = new Properties();
          prop.setProperty(OracleConnection.DCN_QUERY_CHANGE_NOTIFICATION,"false");
          prop.setProperty(OracleConnection.DCN_IGNORE_DELETEOP,"true");
cr = ((OracleConnection) ((WrappedConnection)(((WrappedConnection)conn).getUnderlyingConnection())).getUnderlyingConnection()).registerDatabaseChangeNotification(prop);
               // Add the call back method to the oracle server for the jdbc layer
               logger.info("Adding DCN Listener");
               dcnList = new DCNListener(this);
          dcr.addListener(dcnList);
          // second step: add objects in the registration:
               logger.info("Add Object in the registration");
          stmt = ((WrappedConnection)(((WrappedConnection)conn).getUnderlyingConnection())).getUnderlyingConnection().createStatement();
          // associate the statement with the registration:
               logger.info("Associate the statement with the registration");
          ((OracleStatement)stmt).setDatabaseChangeRegistration(dcr);
          logger.info("Execute registered SQL : "+REGISTERED_SQL);
          rs = stmt.executeQuery(REGISTERED_SQL);

Answer 1

Hi
We are printing the DCN status and registration id in app server log, and it says that registration id is active, and also checked the table USER_CHANGE_NOTIFICATION_REGS.
App server log, after during this issue :
Getting DCN Status --------
DCN RegistrationId (dcr.getRegistrationId()) : 71390
DCN State (dcr.getState()) : ACTIVE
Records from the table :
REGID REGFLAGS CALLBACK OPERATIONS_FILTER CHANGELAG TIMEOUT TABLE_NAME
71390 0 net8://(ADDRESS=(PROTOCOL=tcp)(HOST=IP_ADDRESS)(PORT=XXXX))?PR=0 6 0 4294967295 dcn_queue_table
The registration id at client and at the database matches during this issue and at client log it prints this registration id as ACTIVE during the issue.
According to our logic we read the newly inserted data from table "dcn_queue_table", through select query and and delete the records after the success of read operation .
Hence if there is any record in table dcn_queue_table, then it is an issue for us.
Now during the issue there were records in table, app server didn't receive and notification through the DCN listner thread . Now after 15 min i had updated new record in our application form, and now after 15 min, after the insertion of the new record the notification starts working now for this same DCN RegistrationId 71390.
Please suggest if it look like the issue with app server code that is handling this DatabaseChangeRegistration logic, and not an issue with the database ?