we had, for quite a while, a working situation where a incoming message notifies a plsql procedure, which dequeues and handles the message, resulting in a response message in a different queue
the queue has one subscriber and through dbms_aq.register I registered a plsql callback and all worked fine for about a year
suddenly this stopped working - messages aren't dequeued anymore - for no apparent reason (nothing changed in this part of the database)
I already dropped and recreated the queue table, queues, subscriptions and registered the plsql callback again, but no results
does anyone have a clue where to look (specific sys tables/views, database parameters etc) because I am running out of ideas...
The EMNO (Event Monitor) process is responsible to execute the AQ notifications, in this case your pl/sql callback. This may or may not be your problem. I'm not sure how much help this link will be but it covers Event Monitor issues for various versions of Oracle. https://metalink.oracle.com/metalink/plsql/f?p=130:14:2721106654994549115::::p14_database_id,p14_docid,p14_show_header,p14_show_help,p14_black_frame,p14_font:NOT,105067.1,1,1,1,helvetica