Availability and Failure Statistics Module

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Availability and Failure Statistics Module

Percentage of Service/Component Availability Assumptions

Calculates the percentage of time the Service/Component was available in a certain period of time.

Availability calculations are done either for individual components or for a system. For an example of implementation of availability Business Logic, refer to Case Study 14: Time Accumulation Clock Handling under Appendix 2 in the Implementation Guide.

Availability is calculated as follows:

For each calculation period the calculation method is:
Service or Component Availability equals the Total AST (Agreed Service Time, calculated as the time from the beginning of the calculation period until the end of the calculation period excluding out of timeslot periods) minus the Actual Downtime during the agreed service time (calculated as the accumulation of all down time periods within the calculation period excluding out of timeslot periods) divided by the Total AST multiplied by 100%.

Availability for a system built out of a cluster of resources:

It determines whether the system is available at a certain point of time based on the system logic, which is based on different types of load-balancing between the resources in the cluster.
Component balancing: If at least the number of items based on the Threshold parameter is up, the system is up.

Failure Statistics Assumptions

Failure statistics is constructed to deliver several types of calculations in the Availability domain. These calculations are very similar in nature to Percentage of Service/Component Availability and therefore are implemented in the same module. The module produces the result of the calculation determined by the WhatToCalculate parameter.

If downtime is reported more than once, it is counted as a single failure. In cases when the events are redundant, the downtime is counted once it initially started.
Downtime is considered as a failure when falls within the agreed service time within the timeslot.

Module Interface

The following table lists the parameters.

Name	Description
WhatToCalculate	Determines the calculation result.
Threshold	The number (or percentage) of resources required to be UP for the system to be UP.
ThresholdUnit	The unit for the Threshold (Items or %).
Debug	Determine if in debug mode.

Module Dependencies

The following table lists the included modules.

Name	Description
Log Library (LL)	Library for enhanced logging functionality.
Parameter Kernel Library (PKL)	Library responsible for verifying and populating module parameters.
Parameters Overlay - Basic Action Library (POBAL)	Library responsible for verifying and populating some generic parameters.
Callback Kernel Library (CKL)	Library that enables the callback functionality.
Quick Metric Filtering (QM)	Filtering module required for Quick Metric functionality.
Quick Metric Mapping (QM)	Mapping module required for Quick Metric functionality.

Module Calculations (WhatToCalculate parameter)

MAX – The maximum time period the system was unavailable during the calculation period.
MTBF – Mean Time Between Failures. The average time between failures during the calculation period.
MTTR – Mean Time To Recover. The average elapsed time from the occurrence of a failure to the resolution of the failure.
NumOfFailures – The number of times the system was unavailable during the calculation period.
Availability – The percentage of time the system was available during the calculation period.
PercentOfDowntime - The percentage of time the system was unavailable during the calculation period.
AvailabilityTime – The time that the system was available during the calculation period.
Downtime - The time that the system was unavailable during the calculation period.