That's a pretty open ended qn; it depends on exactly what you are migrating.
1. are you going to try to keep the DB (for example) at the same version/patch level, or take advantage of the move to update or even upgrade to latest version.
(I'm assuming you're keeping that same DB eg Oracle)
2. even though Solaris and Linux are both *nix, you're still going to have to recompile from scratch all of your code.
3. you need experts in both OSes
4. you may have issues with the lang versions of the app code.
5. The default dirs are different between OSes; this will affect the install setup of App & DB and possibly the app code expectations
That's just the very basics; the actual list of qns are specific to your setup and its a long list...
Basically, its a non-trivial exercise, even for a home setup.
For a work system, you'll need extensive planning and testing.