Не апдейтится БД,, не могу понять причину ?

OracleConnection con = new OracleConnection(conStr);
string sqlStr = "UPDATE ANKETAR SET CREDIT=':CREDIT', DATECREDIT=':DATECREDIT', TIMELIMIT=':DATECREDIT', NOMER=':NOMER', DELAYCREDIT=':DELAYCREDIT', COST=':COST', STATUS='3' WHERE UIZ=':UIZ'";
     con.Open();
     OracleCommand cmd = new OracleCommand(sqlStr);
     cmd.Connection = con;
     cmd.CommandType = CommandType.Text;
   
     cmd.Parameters.Add(":CREDIT", OracleDbType.Char, 10);
     cmd.Parameters.Add(":NOMER", OracleDbType.Char, 20);
     cmd.Parameters.Add(":DELAYCREDIT", OracleDbType.Char, 10);
     cmd.Parameters.Add(":UIZ", OracleDbType.Char, 40);
     cmd.Parameters.Add(":COST", OracleDbType.Int32, 20);
     cmd.Parameters.Add(":DATECREDIT", OracleDbType.Date, 8);
     
     cmd.Parameters[":CREDIT"].Value=SumCredit.ToString();
     string Nomer = Session["Nomer"].ToString();
     cmd.Parameters[":NOMER"].Value=Nomer;
     cmd.Parameters[":DELAYCREDIT"].Value=delay.ToString();
     string UIZ = Session["selectedUIZ"].ToString();
     cmd.Parameters[":UIZ"].Value=UIZ;
     DateTime DateCredit = Convert.ToDateTime(Session["DateCredit"]);
     cmd.Parameters[":DATECREDIT"].Value=DateCredit;
     cmd.Parameters[":COST"].Value=Cost;
     int raff = cmd.ExecuteNonQuery();
     con.Close();
     lblError.Text = "сохранено в БД"+raff;