Friday, December 11, 2009

A Short History of DB2 for z/OS – Part 2

Today’s blog entry is a continuation of yesterday’s post in which we began a brief review of the history of DB2 for z/OS. That post covered Versions 1 through 3; so today we pick up our historical review with Version 4.

Version 4 was a very significant milestone in the history of DB2. It was highlighted by the introduction of Type 2 indexes, which removed the need to lock index pages (or subpages, now obsolete). Prior to V4, index locking was a particularly thorny performance problem that vexed many shops. And, of course, I’d be remiss if I did not discuss data sharing, which made its debut in V4. With data sharing, DB2 achieved new heights of scalability and availability unmatched within the realm of DBMS; it afforded users the ability to upgrade without an outage and to add new subsystems to a group “on the fly.” The new capabilities did not stop with there; V4 also introduced stored procedures, CP parallelism, performance improvements, and more. DB2 V4 was, indeed, a major milestone in the history of mainframe DB2.

In June 1997 DB2 Version 5 became generally available. It was the first DB2 version to be referred to as DB2 for OS/390 (previously it was DB2 for MVS). Not as significant as V4, we see the trend of even numbered releases being bigger and more significant than odd numbered releases (of course, this is just my opinion). V5 was touted by IBM as the e-business and BI version. It included Sysplex parallelism, prepared statement caching, reoptimization, online REORG, and conformance to the SQL-92 standard.

Version 6 brings us to 1999 and the introduction of the Universal Database term to the DB2 moniker. The “official” name of the product is now DB2 Universal Database for OS/390. And the Release Guide swelled to over 600 pages! Six categories of improvements were introduced with V6 spanning:
  • Object-relational extensions and active data
  • Network computing
  • Performance and availability
  • Capacity improvements
  • Data sharing enhancements
  • User productivity
The biggest of the new features were SQLJ, inline statistics, triggers, large objects (LOBs), user-defined functions, and distinct types.

Version 6 is also somewhat unique in that there was this “thing” typically referred to as the V6 refresh. It added functionality to DB2 without there being a new release or version. The new functionality in the refresh included SAVEPOINTs, identity columns, declared temporary tables, and performance enhancements (including star join).

March 2001 brings us to DB2 Version 7, another “smaller” version of DB2. Developed and released around the time of the Year 2000 hubbub, it offered much improved utilities and some nice new SQL functionality including scrollable cursors, limited FETCH, and row expressions. Unicode support was also introduced in Db2 V7. For a more detailed overview of V7 (and the V6 refresh) consult An Introduction to DB2 for OS/390 Version 7.

DB2 Version 8 followed, but not immediately. IBM took advantage of Y2K and the general desire of shop’s to avoid change during this period to take its time and deliver the most significant and feature-laden version of DB2 ever. V8 had more new lines of code than DB2 V1R1 had total lines of code!

I don’t want to get bogged down in recent history here outlining the features and functionality of DB2 releases that should be fresh in our memory (V8 and V9). If you really want some details on those refer to these links for them:

An Overview of DB2 for z/OS Version 8


DB2 9 for z/OS Features



Which brings us to today. Most shops should be either running Version 9 in production or planning their migration from V8 to V9. And we are all waiting with baited breath for DB2 X… which hopefully should be announced sometime next year.

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