Mean Time To Repair (MTTR)
Mean Time To Repair (MTTR) is the most common measure of
maintainability. It is the average time required to perform
corrective maintenance on all of the removable items in
a product or system. This kind of maintainability prediction
analyzes how long repairs and maintenance tasks will take
in the event of a system failure.
MTTR also factors in to other reliability and maintainability
predictions and analyses. MTTR can be used in a reliability
prediction in order to calculate the availability of a product
or system. Availability is the probability that an item
is in an operable state at any time, and is based on a combination
of MTBF and MTTR.
more information: http://www.mttr.net/