Hello, and welcome to the party!

There's a lot to unpack there, but I'll try to help a little. These are the questions I spotted.

1. Are data warehouses older technology?

At this...

MY HERO!!!!

Yes, as long as they're actually taking SQL Server backups. There are some...

Thank you Grant, and all, for your advises.

What I also heard is that we need to collect a database workload from production and apply it on our testing environment...

I know it's not free, but it's good. I'd strongly suggest you be ready to invest in your own career and skills. Books are a pretty minor investment in the...

Testing, testing, testing, then test some more.

One thing many people don't know about when upgrading SQL Server using the modern versions (2016+), is Query Store. This is a major tool...

You can look at the backup tables in MSDB, backupset. There's a lot of information there on the type of backup, when it occurred, if it was successful, etc....

Good to hear Lynn. I mean the job thing. Of course I also get excited about selling Redgate software too.

Makes sense.

Yeow!

That's like all the problems.

When I consult on this stuff, the one strong recommendation I make is to get champions at multiple levels on multiple teams. If there are people...

You have to look to multiple metrics. The plan is one, certainly, but after that you look to I/O, CPU, memory, blocked processes, waits.

It would be easier to give a complete answer with the Profiler events and filter. However, on a guess, the process id changed? They're not always the same. If a...

Nah, the plan can be the same for lots of different executions. If it doesn't recompile, regardless of parameters passed, you'll see the same plan used over & over. It's...

So, a hardware change and then behavior changed? When you say right before, you mean several days, several hours, or they pretty much coincide?

We had the experience once where backups slowed down and the problem was a switch going bad. It didn't evidence itself for any other process except our SQL Server backups....