Metrics for Incident management

Answer:

The SLA is one way to ensure incident resolution in a timely manner, but if an organization has other ways to ensure performance (e.g., number of incidents reported in a period), it is achieving the expected results and the customers are satisfied, there is no need to implement SLAs (neither ISO 9001 or ISO 27001 require the establishment of SLAs).

These articles will provide you further explanation about performance measurement:
- How to perform monitoring and measurement in ISO 27001 https://advisera.com/27001academy/blog/2015/06/08/how-to-perform-monitoring-and-measurement-in-iso-27001/
- How to implement the Check phase (performance evaluation) in the QMS according to ISO 9001:2015 https://advisera.com/9001academy/blog/2015/11/17/how-to-implement-the-check-phase-performance-evaluation-in-the-qms-according-to-iso-90012015/