Exceptions in Pl/Sql

Write exceptions to the alert.log or trace files
begin
sys.dbms_system.ksdwrt(2,'ORA-PIPPO prova patrol');
end;

2 Will write the text to the alert log. 
Use 1 instead of 2 to write to the trace file 
Use 3 to write to both. 

10g - Format error and exception
begin
....
exception
  when others then
  begin
    sys.dbms_system.ksdwrt(2,DBMS_UTILITY.FORMAT_ERROR_STACK  );
    sys.dbms_system.ksdwrt(2,DBMS_UTILITY.FORMAT_ERROR_BACKTRACE  );
    RAISE;
  end;
END;

...adding the call stack

sys.dbms_system.ksdwrt(2,DBMS_UTILITY.FORMAT_CALL_STACK);

----- PL/SQL Call Stack -----
  object      line  object
  handle    number  name
0x6f54b8e0       131  procedure MTS_HVIEW_ABN_HISTORY.POPULATE
0x677ca230         1  anonymous block

Please change the owner below

select d.* 
, decode(sign(instr(upper(text), 'EXCEPTION')), 1, '------') matched_line
from (
	select a.owner, a.name, a.type, a.line, a.text
	from dba_source a, ( 
		   select * from dba_source
		   --Change your owner here
		   where owner in ('ALDO', 'ALWORKSHOP')
		   		 and upper(TEXT) like '%EXCEPTION%'
				 and type not in ('JAVA SOURCE')
	) b
	where a.owner = b.owner 
		  and a.name = b.name 
		  and a.type = b.type
		  and a.line in (
		  	  b.line-1, b.line, b.line+1, b.line+2, 
			  b.line+3, b.line+4
		  )
	group by a.owner, a.name, a.type, a.line, a.text
) d
order by owner, name, line

Declaring an exception
  declare
    timeout    EXCEPTION;
    PRAGMA EXCEPTION_INIT (timeout, -25228);
    currWaitSecs number := 0;
    singleWait number := 5;
  begin
    stopApply := false;
    while currWaitSecs <= uptimeSeconds  loop
      begin
        dequeueApplySingle(singleWait);
        currWaitSecs := currWaitSecs + singleWait;
      exception
        WHEN timeout THEN 
        null;
      end;
    end loop;
  end;

Predefined exceptions
ACCESS_INTO_NULL        ORA-06530 Attempted to assign values to the attributes of an uninitialized (NULL) object 
CASE_NOT_FOUND          ORA-06592 None of the choices in the WHEN clauses of a CASE statement is selected and there is no ELSE clause 
COLLECTION_IS_NULL      ORA-06531 Attempt to apply collection methods other than EXISTS to an uninitialized (NULL) PL/SQL table or varray 
CURSOR_ALREADY_OPEN     ORA-06511 Exactly what it seems to be. Tried to open a cursor that was already open 
DUP_VAL_ON_INDEX        ORA-00001 An attempt to insert or update a record in violation of a primary key or unique constraint 
INVALID_CURSOR          ORA-01001 The cursor is not open or not valid in the context in which it is being called 
INVALID_NUMBER          ORA-01722 It isn't a number even though you are treating it like one to trying to turn it into one 
LOGIN_DENIED            ORA-01017 Invalid name and/or password for the instance 
NO_DATA_FOUND           ORA-01403 The SELECT statement returned no rows or referenced a deleted element in a nested table or referenced an initialized element in an Index-By table 
NOT_LOGGED_ON           ORA-01012 You lost your connection to the database 
PROGRAM_ERROR           ORA-06501 Internal PL/SQL error 
ROWTYPE_MISMATCH        ORA-06504 The rowtype does not match the values being fetched, or assigned, to it 
SELF_IS_NULL            ORA-30625 Program attempted to call a MEMBER method, but the instance of the object type has not been intialized. The built-in parameter SELF points to the object, and is always the first parameterpassed to a MEMBER method 
STORAGE_ERROR           ORA-06500 A hardware problem: Either RAM or disk drive 
SUBSCRIPT_BEYOND_COUNT  ORA-06533 Reference to a nested table or varray index higher than the number of elements in the collection 
SUBSCRIPT_OUTSIDE_LIMIT ORA-06532 Reference to a nested table or varray index outside the declared range (such as -1) 
SYS_INVALID_ROWID       ORA-01410 The conversion of a character string into a universal rowid fails because the character string does not represent a valid rowid 
TIMEOUT_ON_RESOURCE     ORA-00051 The activity took too long and timed out 
TOO_MANY_ROWS           ORA-01422 The SQL INTO statement brought back more than one value or row (only one is allowed) 
VALUE_ERROR             ORA-06502 An arithmetic, conversion, truncation, or size-constraint error. Usually raised by trying to cram a 6 character string into a VARCHAR2(5) variable 
ZERO_DIVIDE             ORA-01476 Not only would your math teacher not let you do it. Computer's won't either. Who said you didn't learn anything useful in primary school