Maintenance has to be classified in following categories:
-Declaration and Instauration of the target state e.g. measuring, proofing, counting, triggering, documentation, analyzing
-Measures for retarding of the cutback of the available reserve e.g. resetting, cleaning, replacing, releasing, recording
-Measures for refeeding an unit in the functional state repairing, setting up, replacing, releasing, recording
-Combination of all measures for the increasing of the functional safety of an unit, without changing the claimed function e.g. planning, prevention, approval, accomplishment,
proofing, documentation