Template:System uptime/downtime

Uptime, $${{T}_{UP}}$$
This is the average time the system was up and operating. This is obtained by taking the sum of the uptimes for each simulation and dividing it by the number of simulations. For this example, the uptime is 269.137. To compute the Operational Availability, $${{A}_{o}},$$  for this system, then:


 * $${{A}_{o}}=\frac(eqn 3)$$

CM Downtime, $${{T}_{C{{M}_{Down}}}}$$
This is the average time the system was down for corrective maintenance actions (CM) only. This is obtained by taking the sum of the CM downtimes for each simulation and dividing it by the number of simulations. For this example, this is 30.863. To compute the Inherent Availability, $${{A}_{I}},$$  for this system over the observed time (which may or may not be steady state, depending on the length of the simulation), then:


 * $${{A}_{I}}=\frac{{{T}_{S}}-{{T}_{C{{M}_{Down}}}}}(eqn 4)$$

Inspection Downtime
This is the average time the system was down due to inspections. This is obtained by taking the sum of the inspection downtimes for each simulation and dividing it by the number of simulations. For this example, this is zero because no inspections were defined.

PM Downtime, $${{T}_{P{{M}_{Down}}}}$$
This is the average time the system was down due to preventive maintenance (PM) actions. This is obtained by taking the sum of the PM downtimes for each simulation and dividing it by the number of simulations. For this example, this is zero because no PM actions were defined.

OC Downtime, $${{T}_{O{{C}_{Down}}}}$$
This is the average time the system was down due to on-condition maintenance (PM) actions. This is obtained by taking the sum of the OC downtimes for each simulation and dividing it by the number of simulations. For this example, this is zero because no OC actions were defined.

Total Downtime, $${{T}_{Down}}$$
This is the downtime due to all events. In general, one may look at this as the sum of the above downtimes. However, this is not always the case. It is possible to have actions that overlap each other, depending on the options and settings for the simulation. Furthermore, there are other events that can cause the system to go down that do not get counted in any of the above categories. As an example, in the case of standby redundancy with a switch delay, if the settings are to reactivate the failed component after repair, the system may be down during the switch-back action. This downtime does not fall into any of the above categories but it is counted in the total downtime. For this example, this is identical to $${{T}_{C{{M}_{Down}}}}.$$