Although messages can be received synchronously on a connection, it is often convenient to receive messages asynchronously. You can create a stored procedure that is called when a message has been queued on a particular address. The name of this procedure must be ml_qa_listener_queue, where queue is the message queue. When this procedure exists, the procedure is called whenever a message is queued on the given address.

This procedure is called from a separate connection. As long as a SQL error does not occur while this procedure is executing, the message is automatically acknowledged and committed.

The queue name is part of the QAnywhere address.

• SQL application setup
• QAnywhere message addresses
• Receiving messages asynchronously
• Receiving messages synchronously
• ml_qa_createmessage
• ml_qa_getmessage

The following example creates a procedure that is called whenever a message is queued on the address named executesql. In this example, the procedure assumes that the content of the message is a SQL statement that it can execute against the current database.

CREATE PROCEDURE ml_qa_listener_executesql(IN @msgid VARCHAR(128))
begin
 DECLARE @execstr LONG VARCHAR;
 SET @execstr = ml_qa_gettextcontent( @msgid );
 EXECUTE IMMEDIATE @execstr;
end