Thank you Louis,
I found this note in the wiki.
Using the Query Builder, you can create a database connection definition that can use JDBC or an existing ODBC data source on the Catalog Component server. For ODBC, administrators must define this data source identically on each Catalog Component computer in your implementation. This requirement does not apply to JDBC. Therefore, we recommend JDBC.
Manage Data Objects - CA Service Management - 14.1 - CA Technologies Documentation
It sounds like all we need to do is load the db2 odbc drivers onto the Service Catalog servers and then use the Define Data Source wizard to setup the data object.
Do you know if Type is ignored when ODBC is selected?