trigger oracle execution

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;