The Overall Maintenance Effectiveness is a Unicist Scorecard Indicator (USI) that allows monitoring the effectiveness of maintenance.
The core of the USIs is that they always measure at an operational level the aspects that deal with the reliability, productivity and quality of an activity.
A USI defines the sustainability of an activity considering its competitive environment.
The Reliability of maintenance is defined by the relationship between the maintenance rendered on time and the total maintenance rendered.
The Productivity is defined by the relationship between the productive maintenance hours and the available maintenance hours.
The Quality is defined by the relationship between the flawless maintenance rendered and the total maintenance rendered.
The Overall Maintenance Effectiveness is defined by:
OME = Reliability * Productivity * Quality
The outsourcing of maintenance services requires knowing the OME of the providers.
If you are not aware of the Unicist Standard we strongly recommend reading a homologous example of this type of indicators at:
http://en.wikipedia.org/wiki/Overall_equipment_effectiveness