Recognizing 30 years of DB2, IBM has produced a book, "IBM DB2: The Past, Present & Future." Having read the document myself, I'll relay a few highlights.
This book begins with quotes from many DB2 customers who note the important milestones as well as discuss the value of DB2. I would have to agree with Cuneyt Goksu, who says that the implementation of packages in DB2 V2.3 was a great step. In the book Cuneyt has much more to say on this topic.
Chapter 1, “The History and Growth of IBM’s DB2,” tells an interesting story not only of DB2, but of the leaders and architects who created it and paved the way for its success. Naturally, Don Haderle, DB2's chief architect who became known as “The Father of DB2," is mentioned prominently. I was fortunate to have met Don and hear him speak at IDUG many years ago. It was fun seeing early pictures of him as well DB2 Version 1 development leaders Marilyn Bohl and Bob Jackson.
If your enterprise hasn't yet moved to DB2 10 but is planning to do so, read John Campbell's appropriately titled chapter, “Planning for IBM DB2 10 for z/OS Upgrade.” John brings you highlights from the early release beta program along with some important new features in DB2 10. I feel the "Planning for Real Storage" section is particularly important for DB2 system programmers. I know from listening to both IBM experts and early DB2 10 customers that providing greater real storage to DB2 will greatly reduce your CPU consumption. John thoroughly explains this while providing some formulas to calculate your real storage needs.
I spent many years as a DBA consultant tuning SQL, so I found Terry Purcell's chapter, “DB2 10 for z/OS Query Optimization Update,” most interesting. Terry highlights DB2 10's new access path management features as well as other changes and improvements in the query optimizer. And, since I used to tune legacy CICS transactions, I enjoyed reading about the “NR” In-List Range. This new access method is designed to reduce the index scans used by legacy CICS transactions with scroll logic built into the SQL statement. The book goes into detail on this subject.
If you aren't familiar with DB2's history, I think you'll get a lot from this book. The database's creation and continued evolution is the work of many innovative IBM leaders, developers and researchers. And of course, this history is ongoing, through DB2 10 and beyond.