public void doIUDOperation() {
		 int decide = (int) (Math.random() * 100) % 3;
		 ResultSet rs = null;

		 try {
			switch (decide) {
				 case 0: { //insert
						int numInsert = insertRow(insert);
						pw.println("[NsSampleWork] Thread id - "+thread_id+"; inserted "+numInsert+" row.");
						break;
				 }

				 case 1: { //update
						rs = getMaxKey.executeQuery();
						long updateRow=0;
						if(rs.next())
							updateRow = rs.getLong(1);
						int numUpdate = updateRow(update,updateRow);
						System.out.println("[NsSampleWork] Thread id - "+thread_id+"; updated "+numUpdate+" row with t_key = " + updateRow);
						break;
				 }

				 case 2: { //delete
						rs = getMaxKey.executeQuery();
						long deleteRow =0;
						if(rs.next())
							deleteRow = rs.getLong(1);
						int numDelete = deleteRow(delete,deleteRow);
						System.out.println("[NsSampleWork] Thread id - "+thread_id+"; deleted "+numDelete+" row with t_key = " + deleteRow);
						break;
				 }
		 	}//end of switch()
	 	} catch (Exception e) {
			e.printStackTrace();
		  } finally {
			  try {
			  	if(rs != null)
				  rs.close();
			  } catch (Exception e) {
				  e.printStackTrace();
			    }
		    }
	 }//end of method doIUDOperation()