After ticket re-open SLA should start automatically.How I can do this?
Unfortunately it does not restart automatically on its own. When a ticket is closed, automatically it will close all events. So if you change the status from close to open (or any other "open" type status), the system will not regenerate or start the timer from last event recorded. If the Priority is changed, it will most likley kick it off again depending on how you have it set up. If the ticket is changed from closed to open with no action (meaning no changes such as "priority") then the SLA won't start automatically. This is by design.
A best practice here is that when an analyst has finished with a ticket then he puts it in resolved state. The resolved state should leave the ticket active but suspend service type events. There should be an auto-close policy to then close the ticket within x days if the ticket is left in the resolved state. This gives the customer (Affected End User) a period of time to evaluate the resolution. If the user is not satisfied then he can return it to an open state. Once the ticket is closed is should be considered an artifact and not eligible for re-opening.
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