If update the security patch - MID Server is down?

[Baskarank]

I have few doubts about security patch update:

1.when update security batch is MID server going to down in servicenow?

2. I have upgrade MID server button when I click that button what happend in background ?

3. Instead click upgrade MID server button, It will upgrade automatically, what I do for this?

4.when we update security patch update that time what happend in servicenow?

FYI : 

[Mark Manders]

If all goes well, you don't have to do anything while ServiceNow is patched/upgraded to a new version. The MID server(s) will also auto update. 

In case that can't be done (MID Server offline, config mismatch, etc), there will be a difference between the versions and you can use the 'uprade MID Server' button. If it still doesn't upgrade and the difference is still there, you need to check the MID logs to see what the issue is. 

A couple of months back I had this because the MID Server wasn't allowed access to get the necessary files (new firewall rules at our client prevented that). Changing the rules got that connection back and the server was updated again.

A MID Server can still perform (most) tasks even while on different versions, but it is always best to have them on the same.