create table emp as select * from(
with data as
(
select 100 col1, 101 col2, 'y' primary from dual
union all
select 103 col1, 104 col2, 'n' primary from dual
union all
select 201 col1, 105 col2, 'y' primary from dual
union all
select 100 col1, 101 col2, 'y' primary from dual
) 
select * from data
)
)

create table dept as select * from emp where 1=2;
insert into dept values(100,101,null);
insert into dept values(103,104,null);
insert into dept values(000,656,null);
commit;

select * from emp;
      COL1       COL2 PRIMARY
---------- ---------- -------
       100        101 y      
       103        104 n      
       201        105 y      
       100        101 y      

4 rows selected.

select * from dept;
      COL1       COL2 PRIMARY
---------- ---------- -------
       100        101       
       103        104       
         0        656        

3 rows selected.  

declare
   type typ_emp is table of emp%rowtype;
   var_emp typ_Emp;
cursor c1 is select * from emp;
begin
   open c1;
   loop
      fetch c1 bulk collect into var_emp;
      exit when c1%notfound;
   end loop;
   for i in 1..var_emp.count
   loop
      update dept set primary=var_emp(i).primary
      where dept.col1=var_emp(i).col1
      and dept.col2=var_emp(i).col2;
     
      commit;
   end loop;
   close c1;
exception 
   when others then 
   dbms_output.put_line('came into exception');
end;
/

select * from dept;
      COL1       COL2 PRIMARY
---------- ---------- -------
       100        101 y      
       103        104 n      
         0        656        

3 rows selected.

DECLARE

   TYPE typ_emp IS TABLE OF emp%ROWTYPE;
   var_emp typ_emp;

CURSOR c1 IS
SELECT *
 FROM emp;

BEGIN
 
  OPEN c1;
 
  FETCH c1 BULK COLLECT INTO var_emp;

  FORALL i IN 1..var_emp.count
  UPDATE dept
     SET primary=var_emp(i).primary
   WHERE dept.col1=var_emp(i).col1
     AND dept.col2=var_emp(i).col2;
        
   CLOSE c1;

END;
/

SELECT *
  FROM dept;

      COL1       COL2 PRIMARY
---------- ---------- -------
       100        101 y      
       103        104 n      
         0        656        

3 rows selected.

FORALL i IN 1..var_emp.count
  UPDATE dept
     SET primary=var_emp(i).primary
   WHERE dept.col1=var_emp(i).col1
     AND dept.col2=var_emp(i).col2;

DECLARE

   type typ_primary is table of emp.primary%type index by binary_integer;
   type typ_col1 is table of emp.col1%type index by binary_integer;
   type typ_col2 is table of emp.col2%type index by binary_integer;
   var_primary typ_primary;
   var_col1 typ_col1;
   var_col2 typ_col2;

cursor c1 is
select primary,col1,col2
 FROM emp;

BEGIN
 
  open c1;
  loop 
  fetch c1 bulk collect into var_primary,var_col1,var_col2 LIMIT 1;--may be required incase of large records 
  exit when var_primary.count=0;
  forall i in 1..var_primary.count
  UPDATE dept
     set primary=var_primary(i)
   where dept.col1=var_col1(i)
     and dept.col2=var_col2(i);
        end loop;        
   CLOSE c1;

END;