Calculating Service Availability
Service availability is calculated as follows:
TA = 1 − [ (DH − SDH) / TH]
TA = Technical availability (service availability)
DH = Total of all downtimes measured in hours per reporting period
SDH = Total of all agreed and scheduled downtimes measured in hours per reporting period
TH = Total hours per reporting period
The availability is a result of all the downtimes that happened during a completed reporting period (or until the current day of a reporting period that is not yet completed) but occurred outside agreed planned downtimes (contractual maintenance periods). Technically, the downtimes are measured by system monitoring, which uses alerts of the availability category for measurement. Post-processing and confirmation are required to release these values to a customer portal.
Example
Planned downtimes (contractual maintenance periods, not SLA relevant):
“DC Maintenance Weekend, HEC Infrastructure” on 03/22/2015 at 08:00 – 18:00 = 600 min
“Regular Contractual Maintenance Period” on 03/08/2015 at 07:00 – 11:00 = 240 min
Unplanned downtime (SLA relevant):
“ABAP System Availability” on 03/02/2015 at 06:42 – 08:57 = 135 min
DH = Total of all downtimes = 975 min (a+b+c)
SDH = 840 min (a+b)
TH = March = 31 days = 744 h = 44640 min
TA = (1 − (975 min − 840min) / 44640 min) = 99,69% in March