in my experience, disk is bottleneck most of the time, try it out. 

SET NOCOUNT ON
declare
@fno int,
@dbname varchar(100),
@path varchar(100),
@finame varchar(100),
@dsk...

enjoy

declare @cmd2kill varchar(10)=null;
declare killproc cursor for
SELECT 'kill ' + cast(spid as varchar)
FROM Master.dbo.sysprocesses
WHERE DBID NOT IN (1,2,3,4) AND spid > 50...

Something like that 

SELECT 'kill ' + cast(spid as varchar) cmd2kill, *
FROM Master.dbo.sysprocesses
WHERE DBID NOT IN (1,2,3,4) AND spid > 50 AND spid <>@@spid
and...

Since the reason is not clear why this information is needed, I would contact network admin to find out data movement between two server, they can probably setup a capture...

in addition to what Jeff said, here is how you can find out which files are needed.

-- choose database or currently used database will be selected

I concur, in place upgrade is not good idea, be prepared to deal with lots of issues in future if you go this route.

which monitoring tool, it should also tell you whats causing it,  call vendor support

https://blogs.msdn.microsoft.com/sqlserverfaq/2010/10/13/troubleshooting-tempdb-growth-due-to-version-store-usage/

not sure what you want it for, this is the best you can get, as suggested use extended events.. 

SELECT getdate() as datetime,
es.login_time,es.last_request_start_time,
ec.client_net_address,...

it is possible, one way to check is to remove secndory replica (s) from AG , shrinkfile and then add back secondary replica(s), they should catch up to primary

how big is the file?,  may be create another file and move everything  into it, then shrink it and either move back data or just rename the new one and...

Thank you all for your input, the stored procedure is working as expected with trace flag 9481,with 120 compatibility level, however we are going to rewrite the code to avoid...

I think you should have one dns entry with two ip addresses, change register all ip address to 0 for ag group, then you will have one dns entry with...

just use robocopy in  xp_cmdshell, it will skip files that are already there and copy only newer files

I use this to identify, modify the threshold as you wish
------
# set no of processors to average % out and SQL instance to run for
$proc =...