We want to install SQL Server on a legacy machine which is running Oracle. Is there any reason why they cannot coexist on the same machine?
The "quick" answer is yes as long as there are sufficient resources for all services.
There are no known compatibility problems with running SQL alongside any other Microsoft or 3rd party products... database or otherwise.
Personally I don't really recommend it but I am assuming you have a good reason to do this.
That being said... yes you can. :-)
Travel back to 1999 versions, and it seems they can co-exist.
The same might be true with the modern versions.
I would say: go for it! Perhaps create a new virtual machine, install both applications with the versions that you are interested in, and see how well they play together. Good luck!
Yes, they can. The only issues I've ever seen with Oracle and SQL server not playing nicely with each other was when trying to set up linked servers to Oracle in 64-bit SQL.
Back in 1999 we had SQL Server 7 and Oracle (10?) happily co-habiting on a development box. Can't imagine life has changed much since then.
Been there, done that, although I had both Oracle and SQL Server running on a development system running Windows XP. The system was an 1.2 GHz Pentium system with 1 GB RAM and about 50 GB disk space. Do keep in mind that they will both eat plenty of resources, especially under heavy usage. I just needed them because I was developing some product that had to be able to run on either Oracle or SQL Server. Piece of cake, actually, when you only have three or four users access the system at the same time.
I currently have Oracle 9i & SQL Server 2005 in my dev machine (Note: "dev machine"). To answer your question, based on my experience, yes they can co-exist in one server. But it all comes down to performance and resources issues.
Yes... however, just because you can doesn't mean you should. I'd want to keep them separate with virtual machines if I had to put them on the same physical box, at least on a production box. You're just doing so much to complicate any performance issues, bug hunting, you name it.
Not to mention an upgrade, or problem, with one of the two that effects the system stability (and we all know it can happen) will take down the service for users of databases on both platforms. That's got to be a bad thing.
Memory is a easier problem to manage (since you can dedicate it to the databases) than the attack that the two of them will lay on your disk array. If you are going to double up on one server, please make sure you separate them out so they are pulling from separate disk arrays. Otherwise when they use their temp files for sorting and big queries you will see a ton of spinning disks.
Also make sure you leave enough space in memory not dedicated to the databases. Your operating system will need some breathing room for all the other binaries that are executed that are not included in the database dedicated space. If you don't you will see the operating systems memory manager panic from time to time and switch from standard page swapping into page stealing.