Quite odd combination...
Using SAS/ACCESS to DB2 sounds more straightforward.
I know that there is a possibility to use ODBC in UNIX, but the instructions to make it work seems a bit tricky.
Nevertheless, by registering, do you mean in a Metadata server?
And, can you access these DB2 tables outside SAS on that UNIX box (that is, have you completed the necessary steps in the ODBC setup)?
If so, there are a lot of documentation and papers that describes similar scenarios.
On this site, search for "management console odbc server".