How long do dogs remember things?

Parker was quite naughty tonight

He has an "arch-enemy" but I thought they had become friends, or at least he had grown to tolerate the other dog sharing the same bit of heath as him!

It is a large Labradoodle called Oscar and I think it all started when we were walking round the pitch and putt last year with Cherry on a lead as usual and Oscar ran over to Cherry and started bouncing on her (playfully not aggressively) and Parker warned him off by barking/growling. We carried on walking round and Oscar ran over and bounced on Cherry again, Parker once more warning him off. The 3rd time he ran over to Cherry Parker flew at him, got him on his back and seemed to be biting his neck (Oscar was squealing). I apologised to the owner and got him to check his dog was ok and had not been hurt by Parker. It was fine.

Later on when reading a book about dog behaviour I realised how Parker had behaved was called "ritualised aggression" and was done by an older dog to teach a puppy a lesson (Oscar was a pup then but very big). The dog snaps either side of the other dog's neck but doesn't actually bite.

We have seen Oscar many times since and he keeps away from Cherry now (wise!) and I thought Parker had grown to tolerate him. At first I put him on leash when Oscar was around but they seemed to be ok together though Parker would stop and stare at him when he saw him on the heath (like a cowboy walking into a bar in a western film!).

Tonight he saw Oscar and did the stare thing but then laid down and ignored him. Oscar came a bit nearer and then Parker ran at him and because Oscar just stood there he body-slammed into his shoulder at some force. I think he was expecting him to run away to be honest.

I know now I will have to leash Parker if we see Oscar on the heath again but do you think he remembers Oscar jumping on Cherry? Or is there something about this dog he just doesn't like in the same way that people can have a personality clash?

My husband thinks I'm being fanciful when I say he remembers that Oscar bounced on Cherry but I can't think why else he wouldn't like this dog as Parker is a very sociable dog with other dogs and doesn't go round starting things like he seems to want to do with Oscar!