Issue with AQ notification callback.

Question

Hi,
I'm using OCCI API to subscribe for event notification.
I was able to open subscription and the callback is triggered when the messages are enqueued from DB.
I'm having issues with extracting the data in the callback.
From the oracle doc, I see that only RAW payload is supported if the queue is non-persistent. Different payloads are supported if the queue is persistent and that the user is supposed to explicitly dequeue messages since the messages are not provided as part of NotifyResult argument of the callback.
My question is how do I dequeue messages when the callback is triggered.
I tried to use the consumer with in the callback as below:
Consumer consumer(_connection);
consumer.setConsumerName("fbe_ac1_usr");
consumer.setDequeueMode(oracle::occi::aq::Consumer::DEQ_REMOVE);
consumer.setQueueName("xrfdbo.fbe_ac1_queue");
Message mes = consumer.receive(Message::OBJECT, "CONSOLIDATED_UPDT_MSG_T", "XRFDBO");
PObject* obj = mes.getObject();
I'm getting the exception "21301ORA-21301: not initialized in object mode"
I believe this is due to Environment being created in EVENTS mode to register for subscription.
If I change the mode to OBJECT when I create Environment, I'm getting exception "ORA-01010: invalid OCI operation" while registering for subscription.
Is there any other way to dequeue DB type messages when callback is triggered ?
In order to create a consumer within the callback, I changed my Connection object pointer as static. Is this the right way ?
Thanks

Answer 1

Environment modes are cumulative. You need to define both object and events mode at the same time, which you can do with a bitwise OR of EVENTS and OBJECT.
You are spot on about non-persistent queues. They are deprecated (and slightly buggy, you get the raw payload as an XML document if you dereference the payload pointer in the notification callback function, but I find things go missing, like timestamps for instance), it's replaced by a new kind of persistent queue that behaves similarly to NP queues. I forget the marketing name now, let me go look it up and update the thread.
EDIT: buffered queues.
http://docs.oracle.com/cd/B19306_01/server.102/b14257/aq_intro.htm#sthref76
It's a persistent queuing but the messages live in shared memory until the streams_pool_size is reached. I could be wrong, but I think Oracle built on this to provide continuous query notification.