SQL 2016 Changing Page Verify Impact Recently inherited a new SQL server and after some Blitz (Thanks Brent and team) checks have noticed that some of the DB's are set to Torn_Page or None for the page verify option.  I want to change this to Check_Sum.  

Company policy is raise a change for everything which I have done, I was going to change this early morning as I am sure the impact is very low.  I understand it will flush the proc cache but will it have any other impact on a live system, should it be an out of hours change?
Outside of what you've already noted this should be a low impact change (but hey, anything could happen).

In fact, even if you change the value the checksum won't be calculated and written until the pages and written to disk - which could mean it could take days or weeks to get all of the pages actually changed in a natural lifecycle way (as in you didn't just go around rebuilding indexes to have this immediately take effect).

However, company policy is company policy. Even if there is -5% impact, if anything were to happen then the typical finger pointers will immediately throw out any relevant evidence and logic and start the blame game.

TL;DR: Little to no impact, I'd still put in the change control and "after hours" change due to company policy and CYA.