While going to replatform systems with WinC ++ client / server IBM's RPG on DB2 to target Oracle DB running in a Linux server you are looking for details to setup for building and deploying to the target Java Server however and cannot find these in the PLEX Online help
Particularly for setting up the connectivity via JDBC and build/deployment configuration.

moving systems with WinC ++ client / server IBM's RPG on DB2 to target Oracle DB running in a Linux server

Linux, Oracle database, DB2 Database, CA PLEX

For Development: To build the database objects into Oracle database. 
- Create a ODBC DSN, targeting Oracle database server on hosted Linux machine. 
- Provide this DSN details to Plex IDE while generating/building Database objects. 

For Deployment: To setup Java dispatcher for Oracle database instance. 
- For instance, update obsvr.properties file with Oracle connection details as follows: 
Environment.Default.Driver=oracle.jdbc.driver.OracleDriver 
Environment.Default.DataSource=jdbc:oracle:thin:@[HOST][:PORT]/SERVICE NAME 
Environment.Default.User=User 
Environment.Default.User=Password