Template Software Operability Requirements - Overview

Operability Requirements are the major group within the group of Non-Functional Requirements, often referred as “Quality Attributes”.

Operability Features are best explained by a list of negative examples when those are missing:

• In case of certain errors the the application hangs up and needs complete restart.
• To change a simple parameter you need to restart the application. That takes time, and reduces the uptime.
• During backup the application needs to be shut down (cold backup).
• To activate debug mode (when searching for errors) the application needs to be restarted.
• Debug mode works only system-wide, and not for a single process. Not usable during production load – performance will break down, and disks will run full within short time.
• Adding CPU's does not increase processing capacity because main functionality is served by only one single-threaded process.

Purpose of Operability Requirements is to facilitate reliable operations with sufficient performance. The more requirements are addressed by software, the less repeating work for staff members, who then can pay more attention to improving automated operation and optimizing the system.

Layer	Purpose	Software	Staff
Prevention	Avoid interruptions and downtime	Recording of operational statistics Monitoring for anomalies e.g. unexpected deviations from operational statistics Daily / weekly activities are fully automated (including archiving and purging of old data and log files)	Monthly / Quarterly / Yearly manual review and analysis of operational statistics + activities addressing the findings Manual activities which are not automated yet Adjusting operational parameters
Protection / Defence	Avoid interruptions and downtime	Limiting workload (e.g. Number of requests/second) to design limit to prevent overload
Self-Repair	Minimize duration of interruptions and avoid global downtime	"Build Resilience into the Code" e.g. Automated (but limited) restart of a terminated process (e.g. after loosing database connection). Software supports transparent fail-over to other server.
Troubleshooting / Manual Repair	Minimize duration of interruptions and avoid global downtime	Log files contain meaning full information which is relevant and easy to find. Application software supports activation of debug mode on process level without restart. Other debugging tools are installed. Application supports restarts on process level, without requiring total restart	Understanding the internals of application required for troubleshooting. Experience in use of tools used during troubleshooting – in critical situations time to study documentation would result in breaking SLA's.