What's DB2 UDB?
DB2 UDB stands for DB2 Universal Database and is the former name of both DB2 for Linux, Unix and Windows (LUW), and DB2 for z/OS. It was introduced about 15 years ago, but it has now been dropped from the list of terms used to identify current products. On Linux, Unix and Windows, the following DB2 versions exist:
The right version for you will depend on your hardware and usage requirements. In any case, I recommend that you download DB2 Express-C. It's absolutely free and production ready. Its only limitation is that it'll use a maximum of 16 GB of RAM and 4 CPU cores only, independently from your hardware. Purchasing 24/7 support for less than $3K a year, enables DB2 to use up to 4 GB of RAM and adds High Availability and Disaster Recovery (HADR), plus SQL Replication.