Sqlcode 100 does not come with exception

Question

I have following query
SELECT a.col1 into v_acc_account FROM account_t a
WHERE a.col1=<input paramter> FOR UPDATE OF a.col1 NOWAIT;
The statement returns sqlcode of 100 and does not throw exception
From oracle documentation I understand that the errorcode is accompanied by an exception. What may be the reason behind this behavior.
The return code 100 explains 'DATA NOT FOUND", we have data for the select query.
Data not found means, the select is failing or the locks not available.
any help much appreciated
Regards,
Nandish

Answer 1

The code does not make much sense.
What is the actual problem to address - obtain a row lock using several retries with a 2 sec delay between each retry?
I would suggest a modularised approach like the following - with code that is easy to read, understand and maintain:
SQL> create or replace procedure LockEmpForUpdate(
  2          empID number,
  3          waits integer default 5,
  4          waitSecs integer default 2 ) is
  5 
  6          RESOURCE_BUSY   exception;
  7          pragma exception_init( RESOURCE_BUSY, -54 );
  8 
  9          loopCnt integer;
10          rID     rowid;
11  begin
12          loopCnt := 1;
13          while (loopCnt <= waits ) loop
14                  begin
15                          loopCnt := loopCnt + 1;
16 
17                          select
18                                  e.rowid into rID
19                          from    emp e
20                          where   e.empno = empID
21                          for update
22                          nowait;
23 
24                  exception when RESOURCE_BUSY then
25                          if loopCnt <= waits then
26                                  DBMS_LOCK.Sleep( waitSecs );
27                          end if;
28                  end;
29          end loop;
30 
31          if rID is null then
32                  raise_application_error(
33                          -20000,
34                          'Failed to obtain a row lock on employee '||empID
35                  );
36          end if;
37 
38  end;
39  /
Procedure created.
SQL>
SQL> --// this employee is locked in another session via an update
SQL> exec LockEmpForUpdate( empID => 7369 )
BEGIN LockEmpForUpdate( empID => 7369 ); END;
ERROR at line 1:
ORA-20000: Failed to obtain a row lock on employee 7369
ORA-06512: at "BILLY.LOCKEMPFORUPDATE", line 32
ORA-06512: at line 1
SQL> --// this employee is not locked
SQL> exec LockEmpForUpdate( empID => 7782 )
PL/SQL procedure successfully completed.
SQL>