PL/SQL Oracle: Ejemplo del uso del "For Update Of" y "Current Of"

getCodeSeq.sql

Create Or Replace Function getCodSeq(xcodseque In Varchar2,xtam In Number Default Null) Return Varchar2 Is
  xvalseque sfad012t.valseque%Type;
  xcodprefi sfad012t.codprefi%Type;
  xseque    Varchar2(50);
  Cursor c1 Is
    Select nvl(valseque, 0) + nvl(incseque, 1), codprefi 
    Into   xvalseque, xcodprefi 
    From   sfad012t 
    Where  codseque = xcodseque
    For Update Of valseque;
Begin
  Open  c1;
  Fetch c1 Into xvalseque, xcodprefi;
  If c1%found Then
    Update sfad012t 
    Set    valseque = xvalseque
    Where  Current Of c1;
  End If;
  Close c1;
  xseque := ltrim(rtrim(xcodprefi || lpad(xvalseque, nvl(xtam, length(xvalseque)), '0')));
  Return xseque;
End getCodSeq;