oracle trigger

1CREATE [OR REPLACE ] TRIGGER trigger_name  
2{BEFORE | AFTER | INSTEAD OF }  
3{INSERT [OR] | UPDATE [OR] | DELETE}  
4[OF col_name]  
5ON table_name  
6[REFERENCING OLD AS o NEW AS n]  
7[FOR EACH ROW]  
8WHEN (condition)   
9DECLARE 
10   Declaration-statements 
11BEGIN  
12   Executable-statements 
13EXCEPTION 
14   Exception-handling-statements 
15END; 

1CREATE OR REPLACE TRIGGER my_schema.trigger_name AFTER LOGON ON DATABASE
2BEGIN
3    INSERT INTO my_log_table
4    VALUES (USER AS CONNECTED_USER,
5        sys_context('USERENV', 'SESSIONID') AS SESSION_ID,
6        substr(sys_context('USERENV', 'OS_USER'), 1, 50) AS OS_USER,
7        substr(sys_context('USERENV', 'HOST'), 1, 30) AS HOST,
8        SYSDATE AS LOGON_DATE);
9END;
10ALTER TRIGGER my_schema.trigger_name ENABLE;