Advanced Queuing - Oracle

Propagation Issues
Propagation Issues
Propagation makes use of the system queue aq$_prop_notify_X, where X is the
instance number of the instance where the source queue of a schedule resides, for
handling propagation run-time events. Messages in this queue are stored in the
system table aq$_prop_table_X, where X is the instance number of the instance
where the source queue of a schedule resides.
Execute Privileges Required for Propagation
Propagation jobs are owned by SYS, but the propagation occurs in the security
context of the queue table owner. Previously propagation jobs were owned by the
user scheduling propagation, and propagation occurred in the security context of
the user setting up the propagation schedule. The queue table owner must be
granted EXECUTE privileges on the DBMS_AQADM package. Otherwise, the Oracle
snapshot processes will not propagate and generate trace files with the error
identifier SYS.DBMS_AQADM not defined. Private database links owned by the queue
table owner can be used for propagation. The user name specified in the connection
string must have EXECUTE access on the DBMS_AQ and DBMS_AQADM packages on
the remote database.
The Number of Job Queue Processes
Caution: The queue aq$_prop_notify_X should never be
stopped or dropped and the table aq$_prop_table_X should
never be dropped for propagation to work correctly.
The scheduling algorithm places the restriction that at least two job queue processes
be available for propagation. If there are nonpropagation-related jobs, then more job
queue processes are needed. If heavily loaded conditions (a large number of active
schedules, all of which have messages to be propagated) are expected, you should
start a larger number of job queue processes and keep in mind the need for
nonpropagation jobs as well. In a system that only has propagation jobs, two job
queue processes can handle all schedules. However, with more job queue processes,
messages are propagated faster. Since one job queue process can propagate
messages from multiple schedules, it is not necessary to have the number of job
queue processes equal to the number of schedules.
Managing AQ 4-11