Oracle is extremely good at coming in, completely hosing everything, then disappearing and sending you a $350/hr invoice for the privilege. Their consultants seem to tread the line between totally incompetent and actively malevolent surprisingly well.
Do you have anything to back your opinion or you had just one bad experience with Oracle consultant and now generalize to tens or hundreds of thousands of cases that you have absolutely no knowledge about?
On my part I only have very positive experience with Oracle consultants, but this is only my opinion based on just a few interactions.
I worked for a Fortune 500 healthcare company that used both Oracle and IBM consultants extensively. I had exactly two positive experiences with Oracle consultants where they delivered as promised and maybe four or five where they delivered but took longer/went over budget/etc to the point where I feel we lost value in the long run. And maybe two dozen experiences that were as I described initially.
So in my experience somewhere between 5-8% will be worth it.
At my last job, we used to have an Oracle-acquired storage product in a rather critical part of our stack. It was having some performance problems one night, during a peak traffic period. It may even have been Cyber Monday; I don't remember exactly.
Our then systems team lead called Oracle support, and was advised by the support rep — a third tier rep, mind you, because we had priority support, and had the call escalated when the first guy couldn't do anything — to run an on-board low-level diagnostic. He confirmed with the phone rep three separate times that running such a check would be safe to do with live, mounted filesystems, and would not adversely impact operations. He was answered in the affirmative each time.
He hit enter. The site went down. $.75mm in lost revenue over the next 8-10 hours, unfucking that pretty little mess.
When in doubt, refuse and escalate. It's your systems! Especially with Oracle support, who have a particularly bad reputation.
Honestly, Oracle's reputation is mud. Ever since I saw the Oracle Chief CSO's presentation on security which used biblical parables as principles for securing environments I've been even more wary of accepting any advise on face value from any Oracle employer...