2 Workspace Manager Events

Example 2-2 Granting Privileges for Queue Access

-- Do the following while connected as SYSDBA.
-- These privileges are required for the user to execute AQ packages.
grant execute on DBMS_AQ to SCOTT ;
grant execute on DBMS_AQADM to SCOTT ;

-- Grant privilege to SCOTT for subscribing to the event queue.
exec DBMS_AQADM.GRANT_SYSTEM_PRIVILEGE('MANAGE_ANY','SCOTT') ;

-- Grant privilege to SCOTT to dequeue events. (As an alternative, you could use
-- DBMS_AQADM.GRANT_QUEUE_PRIVILEGE to grant the DEQUEUE privilege on
-- WMSYS.WM$EVENT_QUEUE.)
exec DBMS_AQADM.GRANT_SYSTEM_PRIVILEGE('DEQUEUE_ANY','SCOTT') ;

Example 2-3 Rule-Based Subscription for Workspace Manager Events

rem =================================================
rem Create queue subscribers
rem Register for MergeWorkspace event when
rem a workspace is merged to LIVE
rem =================================================

connect scott/tiger

DECLARE
    subscriber sys.aq$_agent;
BEGIN
    subscriber := sys.aq$_agent('MERGE_LISTENER', NULL, NULL);
    dbms_aqadm.add_subscriber(
      queue_name => 'WMSYS.WM$EVENT_QUEUE',
      subscriber => subscriber,
      rule => 'tab.user_data.event_name = ''WORKSPACE_MERGE_WO_REMOVE''
               and tab.user_data.parent_workspace_name = ''LIVE''');
END;
/

Example 2-4 Listening for a Workspace Manager Event

rem ==============================================================
rem The following example shows how an application can listen for
rem an event. Explicit dequeue must be performed to get the actual
rem event parameters. The user SCOTT must have sufficient privileges 
rem as described in the "Access Control" section.
rem ==============================================================

connect scott/tiger

set serveroutput on

DECLARE
 qlist dbms_aq.aq$_agent_list_t;
 agent_w_msg sys.aq$_agent;
 listen_timeout exception;
 pragma exception_init(listen_timeout, -25254);
BEGIN
 qlist(0) := sys.aq$_agent('MERGE_LISTENER', 'WMSYS.WM$EVENT_QUEUE', NULL);

 dbms_output.put_line ('Listening on event queue.');

 BEGIN

 DBMS_AQ.LISTEN(
         agent_list => qlist,
         wait => 30,
         agent =>  agent_w_msg);

         dbms_output.put_line(agent_w_msg.name) ;

         /* The event can be dequeued here to get the event data */

 EXCEPTION
        when listen_timeout THEN
                null;
 END;

END;
/

Example 2-5 Receiving Asynchronous Notification of Events

rem =====================================================
rem Example of how to register for a callback to the event
rem queue on behalf of a subscriber. Subscriber has already
rem been defined in previous section. The callback is
rem invoked by the AQ framework whenever an event satisfying the
rem rule for the subscriber occurs. The minimum values for
rem the following init.ora parameters should be set as follows.
rem   aq_tm_processes = 1
rem   job_queue_processes = 2
rem The user SCOTT must have sufficient privileges.
rem ===========================================================

CONNECT scott/tiger

CREATE TABLE merge_log
(
  event_name      varchar2(30),
  workspace_name  varchar2(30),
  parent_workspace_name varchar2(30),
  user_name       varchar2(30)
);

CREATE OR REPLACE PROCEDURE scott.event_callback(
   context RAW , reginfo sys.aq$_reg_info, descr sys.aq$_descriptor, 
   payload VARCHAR2,  payloadl NUMBER)
AS
    deq_msgid           RAW(16);
    dopt                dbms_aq.dequeue_options_t;
    mprop               dbms_aq.message_properties_t;
    event               WMSYS.WM$EVENT_TYPE;
    no_messages         exception;
    pragma exception_init(no_messages, -25228);

BEGIN
    dopt.consumer_name := 'MERGE_LISTENER';
    dopt.wait := 30;
    dopt.msgid := descr.msg_id;

    dbms_aq.dequeue(
        queue_name => 'WMSYS.WM$EVENT_QUEUE',
        dequeue_options => dopt,
        message_properties => mprop,
        payload => event,
        msgid => deq_msgid);

    INSERT INTO merge_log VALUES (event.event_name, event.workspace_name,
      event.parent_workspace_name, event.user_name);

    /* Note: If there are additional parameters stored in
       "aux_params" attribute, it can be accessed using 
       event.aux_params(1).name, event.aux_params(1).value, 
       event.aux_params(2).name … and so on. The number of 
       parameters can be accessed using event.aux_params.count 
       when aux_params is not null.
     */
END;
/

grant execute on scott.event_callback to public ;

rem ==================================================
rem Register a callback for the event
rem Queue name and subscriber name have to be specified
rem while registering for a callback
rem ==================================================

DECLARE
  reginfo1            sys.aq$_reg_info;
  reginfolist         sys.aq$_reg_info_list;
BEGIN
  reginfo1 := sys.aq$_reg_info('WMSYS.WM$EVENT_QUEUE:MERGE_LISTENER',1,'plsql://scott.event_callback?PR=1',HEXTORAW('FF'));

  reginfolist := sys.aq$_reg_info_list(reginfo1);

  sys.dbms_aq.register(reginfolist, 1);

  COMMIT;

END;
/