If a controller loses power, it loses the configuration stored in RAM. Controller RAM contains the downloaded configuration as well as online parameter changes that you make following the download. The controller provides features that prevent the loss of configuration data and certain online changes in the event of a power loss:
Cold restart - retains a copy of the last download script in cold restart memory. Cold restart memory is retained through a power loss. When power is restored, the controller automatically restarts using the download script in cold restart memory. Uploaded online changes made to modules persist through temporary power failure if the cold restart feature was previously enabled and power was restored within time limit configured for cold restart.
Restore parameter values after restart - retains the online parameter value changes for certain parameters in nonvolatile memory.