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About Oracle
dbms_alert
The
dbms_alert package is
created by executing the
catproc.sql file and is
owned by SYS. Once granted the
execute privilege to
dbms_alert, it can be
executed by any software
component that can call a stored
procedure including SQL*Plus,
Java and Pro*C.
The
dbm_alert procedure is
rarely used.
The
dbms_alert package provides
a mechanism for the database to
notify a client (anything
listening) of an event
asynchronously, which means that
the application does not need to
periodically check for the
occurrence of events.
With
dbms_alert, when an event
occurs, a notification will be
sent. Prior to
dbms_alert, developers created a
polling process that checked the
status of something on the
database, like a completed job,
by checking for a table value
that the process had just
updated. dbms_alert
renders such techniques obsolete
and is one of the best Oracle
supplied packages.
The
dbms_alert package is even
more helpful when dealing with 3
tier web applications – client,
web server, and database. Web
applications are “stateless” by
nature, meaning that the web
server processes a request and
it's done - there is no tethered
connection like we're accustomed
to with SQL*Plus, Oracle
Applications, or SAP R/3. The
Oracle dbms_alert
provides a way for the database
to initiate contact with the web
server, who in turn can notify
clients attached to it.
Description of the
DBMS_ALERT package:
PROCEDURE DBMS_ALERT.REGISTER
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
NAME VARCHAR2 IN
PROCEDURE DBMS_ALERT.REMOVE
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
NAME VARCHAR2 IN
PROCEDURE DBMS_ALERT.REMOVEALL
PROCEDURE DBMS_ALERT.SET_DEFAULTS
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
SENSITIVITY NUMBER IN
PROCEDURE DBMS_ALERT.SIGNAL
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
NAME VARCHAR2 IN
MESSAGE VARCHAR2 IN
PROCEDURE DBMS_ALERT.WAITANY
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
NAME VARCHAR2 OUT
MESSAGE VARCHAR2 OUT
STATUS NUMBER(38) OUT
TIMEOUT NUMBER IN DEFAULT
PROCEDURE DBMS_ALERT.WAITONE
Argument Name Type In/Out Default?
------------------------------ ----------------------- ------ --------
NAME VARCHAR2 IN
MESSAGE VARCHAR2 OUT
STATUS NUMBER(38) OUT
TIMEOUT NUMBER IN DEFAULT
See these
related noted on
dbms_alert:
dbms_alert - Oracle Utilities
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