The Oracle Transparent Gateway for DB2 (TG4DB2) is installed on the mainframe. It provides an Oracle listener and translator. Your clients and Oracle databases don't need any new software; you can connect to the DB2 database just like you would any other Oracle database.
If you want an Oracle database to be able to query or work with data in a DB2 database, then create a database link in your Oracle database.
Suppose you have DB2 user BOB with table EMP, and in Oracle you created a db_link named TG4DB2.WORLD. Then you can issue commands like SELECT * FROM BOB.EMP@TG4DB2.WORLD.
1. DB2 timestamps will appear to your Oracle database and clients as CHAR(26). I know of no way around this; it is a function of the TG4DB2 translator.
2. If an Oracle DBMS_JOB will pull data from DB2 across an Oracle database link, then the link must specify a username and password. It cannot be anonymous (i.e., the following is not supported when using DBSM_JOBs "create database link test.world using 'test.world';").