Advanced Queuing - Oracle

JMS Propagation
processes can be skewed based on the arrival rate of messages in the different
source topics. If one process is overburdened with several active schedules while
another is less loaded with many passive schedules, propagation automatically
re-distributes the schedules among the processes such that they are loaded
uniformly.
Example Scenario
In the BooksOnLine example, the OE_bookedorders_topic is busy since
messages in it are propagated to different shipping sites. The following example
code illustrates the calls supported by enhanced propagation scheduling for error
checking and schedule monitoring.
Example Code
CONNECT OE/OE;
/* get averages
select avg_time, avg_number, avg_size from user_queue_schedules;
/* get totals
select total_time, total_number, total_bytes from user_queue_schedules;
/* get maximums for a window
select max_number, max_bytes from user_queue_schedules;
/* get current status information of schedule
select process_name, session_id, instance, schedule_disabled
from user_queue_schedules;
/* get information about last and next execution
select last_run_date, last_run_time, next_run_date, next_run_time
from user_queue_schedules;
/* get last error information if any
select failures, last_error_msg, last_error_date, last_error_time
from user_queue_schedules;
Exception Handling During Propagation
When a system errors such as a network failure occurs, AQ will continue to attempt
to propagate messages using an exponential back-off algorithm. In some situations
that indicate application errors AQ will mark messages as UNDELIVERABLE if there
is an error in propagating the message.
12-92 Oracle9i Application Developer’s Guide - Advanced Queuing