upgrade downtime

[MARIEM QARA]

• Upgrade with Downtime: it is mentioned in the doc that downtime may be occurred for major update, How frequently do these major updates occur? Even though the schedule might not be fixed, can you provide an approximate frequency?"
• Communication: Regarding Major updates  :the changes may be communicated in advance to customers /stakeholders ' on what criteria is this based?"
• Feature Activation: "On what basis are new features activated by default or not? If they are not activated by default, when and by whom are they activated? Is it the customer who decides?"

[John Funk]

Hi Mariem - Welcome to the Atlassian Community!

I can tell that it is not too frequent from my experience. But for details, you would need to contact Atlassian Support. 

https://support.atlassian.com/contact/#/

[Joseph Chung Yin]

@MARIEM QARA 

Welcome to the community.  Your best recommendation is contacting Atlassian Support (https://support.atlassian.com) for further information.

I am not aware if it happens on a frequent basis.  In regards to any downtimes with Atlassian Cloud envs - you can also check to find their products' statuses - https://status.atlassian.com/

For Features (ones that before they are GA released to all customers), each site admins can enable or disable the features as needed.

Hope this also helps.

Best, Joseph Chung Yin