Download DBMS_PIPE

Intersession Communication
Oracle Database PL/SQL 10g Programming
Chapter 11
Intersession Communication



2006
Intersession Communication Definition
DBMS_PIPE Built-in Package
DBMS_ALERT Built-in Package
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 2
Intersession Communication
DBMS_PIPE

Interactive intersession communication is:





2006
The process of sending messages from one
open session in the database to another.
The process works by accessing a messaging
buffer, known as a pipe.
Pipes are FIFO (First-in and last-out) queues.
The pipes can be local, private, and public.
The process uses the DBMS_PIPE built-in
package to send and receive messages.
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 3
Intersession Communication
DBMS_PIPE: Local Buffer
Local Buffer
Write to
Local Buffer
2006
Read from
Local Buffer
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 4
Intersession Communication
DBMS_PIPE: Local Buffer Write
DECLARE
message
VARCHAR2(30);
success
INTEGER;
BEGIN
message := DBMS_PIPE.UNIQUE_SESSION_NAME;
DBMS_PIPE.RESET_BUFFER;
DBMS_PIPE.PACK_MESSAGE(message);
DBMS_OUTPUT.PUT_LINE('Message ['||message||'] ');
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 5
Intersession Communication
DBMS_PIPE: Local Buffer Read
DECLARE
message
VARCHAR2(30);
success
INTEGER;
BEGIN
DBMS_PIPE.UNPACK_MESSAGE(message);
DBMS_OUTPUT.PUT_LINE('Message ['||message||'] ');
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 6
Intersession Communication
DBMS_PIPE: SGA Named
Pipe
Named Pipe
2006
Local Buffer
Local Buffer
Write to
Local Buffer
Read from
Local Buffer
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 7
Intersession Communication
DBMS_PIPE: Create a Pipe
DECLARE
message_pipe
VARCHAR2(30) := 'PLSQL$MESSAGE_INBOX';
success_size
INTEGER
:= 2000;
retval
INTEGER;
'||message||'
BEGIN
retval := DBMS_PIPE.CREATE_PIPE();
IF (retval = 0) THEN
DBMS_OUTPUT.PUT_LINE('Message ['||message||'] ');
END IF;
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 8
Intersession Communication
DBMS_PIPE: Write to a Pipe
DECLARE
flag INTEGER;
BEGIN
DBMS_PIPE.PURGE('PLSQL$MESSAGE_INBOX');
DBMS_PIPE.PACK_MESSAGE('MESSAGE');
DBMS_PIPE.SEND_MESSAGE('PLSQL$MESSAGE_INBOX');
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 9
Intersession Communication
DBMS_PIPE: Read from a
Pipe
DECLARE
message VARCHAR2(4000);
flag INTEGER;
BEGIN
DBMS_PIPE.RESET_BUFFER;'||message||'
-- Force immediate read of pipe.
flag := DBMS_PIPE.RECEIVE_MESSAGE('PLSQL$MESSAGE_INBOX',0);
DBMS_PIPE.UNPACK_MESSAGE('MESSAGE');
DBMS_PIPE.SEND_MESSAGE('PLSQL$MESSAGE_INBOX');
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 10
Intersession Communication
DBMS_ALERT

Event-driven intersession communication is:




DBMS_ALERT built-in sends messages through a pipe:
The transaction-based DBMS_ALERT lets a database
trigger send an alert message to an implicit public
pipe.
DBMS_ALERT uses a publish-and-subscribe pattern
where multiple sessions can register interest in an
alert.
Subscribers, those who register:


2006
Wait on the event for a polling interval.
Read ONLY the last message received by the pipe because it
is a single element queue.
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 11
Intersession Communication
DBMS_ALERT: Publish on Event
CREATE OR REPLACE TRIGGER signal_message
AFTER INSERT
OF message_id, message
ON messages
'||message||'
FOR EACH ROW
BEGIN
IF :old.message_id IS NULL THEN
DBMS_ALERT.SIGNAL('EVENT_MESSAGE_QUEUE',:message);
END IF;
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 12
Intersession Communication
DBMS_ALERT: Subscribe
BEGIN
-- Subscribe to an alert event.
DBMS_ALERT.REGISTER('EVENT_MESSAGE_QUEUE');
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 13
Intersession Communication
DBMS_ALERT: Catch
DECLARE
message VARCHAR2(4000);
flag INTEGER;
BEGIN
'||message||'
DBMS_ALERT.WAITONE('EVENT_MESSAGE_QUEUE'
,message,status,30);
END;
/
2006
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 14
Summary





2006
Database Trigger Concepts
DDL Triggers
DML Triggers
Instead-of Triggers
System or Database Event Triggers
Oracle Database PL/SQL 10g Programming
(Chapter 11)
Page 15