2.1. DP Classes - Redundancy Levels

Classification societies set the standards for DP system classes. Accoding to DNV 

Class 0: Manual position control and automatic heading control

Class 1: Automatic and manual position and heading control. No redunancy =>Loss of position can occur in the event of a single fault.

Class 2: Automatic and manual position and heading control. Loss of position should not occur from a single fault of an active component or system such as generators, thrusters, switchboards, remote control valves etc. However, loss of position can occur after failure of static components such as cables, pipes, manual valves etc.

Class 3: Automatic and manual position and heading control. Loss of position should not occur from any single failure including a complete burn fire subdivision or flooded watertight compartments. Reduntand and seperated components. 

Table of Equivalent DP Classes, DNV, ABS, IMO

2.2. Codes and guidelines

Classifications societies offer classification standards and guidelines. Most renowed are:

DNV: Dynamic Positioning Vessel Design Philosophy Guidelines, DNV-RP-E306
  Dynamic Positioning Systems, Updated July 2013
ABS: Guide for Dynamic Positioning Systems, Updated July 2014
IMCA: IMCA M 103 Rev. 1, December 2007

Further Reading on Dynamic Positioning

http://www.dynamic-positioning.com/pastproceedings.cfm

http://www.imca-int.com/marine-division/dynamic-positioning.aspx