PL/SQL notification / DBMS_AQ.REGISTER

Question

There have been a number of discussions on this forum about PL/SQL notifications. I'm running
into the same problem:
- create the notification procedure
- register the procedure
- enqueue a message
- NOTHING HAPPENS
It seems that the notification procedure is not executed.
The discussions on this forum were all inconclusive. Did anybody get this to work? If yes, can
you post an example (i.e. a script that creates the queue, create the procedure, registers the
procedure and enqueues a message)?
Is there a table/view that contains the registrations?
What system parameters are relevant to this functionality?
Where are errors in calling the notification procedure logged?

Answer 1

There are few problems that I can see with your code.
Your callback procedure header should look like this:
create or replace procedure QCallBack1(
context RAW,
reginfo SYS.AQ$_REG_INFO,
descr SYS.AQ$_DESCRIPTOR,
payload VARCHAR2,
payloadl NUMBER) is
BEGIN
END ;
And your callback notification does not include the name of the QUEUE subscriber. The first parameter
to the AQ$_REG_INFO should be of this format: <QUEUE ADMIN>.<QUEUE_NAME>:<QUEUE SUBSCRIBER>
When you say this:
sys.aq$_reg_info('myprofile.Que1',dbms_aq.namespace_aq, 'plsql://myprofile.QCallBack1', hextoraw('FF'));
You are not putting the name of the queue subscriber into the first parameter.
Also, Your callback notification URL must be like this:
'plsql://<user containing the callback proc>.<name of the callback proc>?PR=1'
Note that if the callback procedure is in another schema, you must grant EXECUTE priv. to the user
where the QUEUE has been setup.
Hallo,
I have got the same problem as Erwin Groenendal. I wrote single user que and procedures to enque and deque as simple as I can do.
pseudocode:
1. create and start que - no error
2. create proc for callback in pl/sql - no error
3. register callback - no error
4. enque message - noerror (no callback called)
5. deque message - noerror
in callback procedure I am writing into my own table with one varchar2 column to determine if the callback was processed.
My register procedure looks like: (pseudocode point 3)
procedure Register
is
XRegProc sys.aq$_reg_info;
XRegList sys.aq$_reg_info_list;
begin
XRegProc := sys.aq$_reg_info('myprofile.Que1', dbms_aq.namespace_aq, 'plsql://myprofile.QCallBack1', hextoraw('FF'));
XRegList := sys.aq$_reg_info_list(XRegProc);
dbms_aq.register(XRegList, 1);
end;
in definition variable XRegProc I tryed all possibilities like:
'plsql://myprofile.QCallBack1'
'plsql://myprofile.QCallBack1?PR=0'
'plsql://QCallBack1'
'plsql://myprofile.QCallBack1'
and so on.
The Callback looks like:
procedure QCallBack1(
context out raw,
reginfo out sys.aq$_reg_info,
descr out sys.aq$_descriptor,
payload out raw,
payloadl out number)
is
begin
insert into MyOwnTable (my_text) values ('Message notification callback called.');
commit;
end;
with compilation i have not problems. I am running oracle 9i release 2.
the enque procedure looks like:
procedure put(
APayload in raw,
ACorrelation in varchar2)
is
XEnq_opts dbms_aq.enqueue_options_t;
XMsg_props dbms_aq.message_options_t;
XMsg_id raw(16);
begin
XMsg_props.correlation := ACorrelation;
dbms_aq.enqueue('Que1', XEnq_opts, XMsg_props, APayload, XMsg_id);
commit;
end;
All rights are corectly sets under SYSTEM user.
Please help somebody why it does not work. I not see problem byt I need to call some procedure when new message arive into que. I need to have paralel process, I can not solve it with loops and so on.
Thanks for every ideas. In next week I can show you source code. Today I can not.
Regards, Zdenek.
For Oracle9i and above DBMS_AQ.REGISTER can be used for PL/SQL callback notification.
If running earlier version of Oracle, use DBMS_AQ.LISTEN to get a similar functionality.
It depends upon the URL that you specify while registering, that decides if callback will be executed or
not.
If you post the code fragment(s) of how you created the notification procedure and how you registered it,
maybe we can look to see if it is correct.
There have been a number of discussions on this forum about PL/SQL notifications. I'm running
into the same problem:
- create the notification procedure
- register the procedure
- enqueue a message
- NOTHING HAPPENS
It seems that the notification procedure is not executed.
The discussions on this forum were all inconclusive. Did anybody get this to work? If yes, can
you post an example (i.e. a script that creates the queue, create the procedure, registers the
procedure and enqueues a message)?
Is there a table/view that contains the registrations?
What system parameters are relevant to this functionality?
Where are errors in calling the notification procedure logged?