Monday, April 20, 2020

Db2 for z/OS and Managing Database Changes - Part 2

In part 1 of our multi-part series on Db2 for z/OS database change management, we provided an overview of the three types of database change that can be undertaken. In today's post, we are going to examine the first type of change -- the simple database change -- in a little more depth.

Simple database changes are the easiest to implement. A simple database change, typically implemented using the ALTER statement, can be executed immediately upon request. The change is made immediately but may require additional actions to fully implement. For example, if you add a nullable column at the end of a table using ALTER TABLE ADD COLUMN the change is made immediately. For all intents and purposes, the addition is complete. However, under the covers, Db2 has not expanded the storage for each row to include space for the column. This happens as the column is accessed and used, or when the table space is reorganized. Applications can use and access the new column without knowing this, however, so the change is immediate; housekeeping to implement the change entirely may occur over time.

Additional examples of simple, immediate changes are most CREATE and DROP statements; altering STOGROUPs; altering most default parameters for databases, table spaces, indexes, and STOGROUPs; renaming tables (packages are invalidated but privileges and indexes are maintained)[1]; renaming indexes; adding a column at the end of a table[2]; changing the data type[3], precision scale of length of a column[4]; identity column parameters, adding and dropping versioning to a temporal table, adding and dropping constraints[5]; activating and deactivating row access control; adding, dropping, and exchanging clone tables; altering, dropping, and refreshing materialized query tables[6]; creating, dropping, and renaming global temporary tables; altering most aspects of user-defined functions and stored procedures; and changing or dropping labels on tables, aliases, and columns. 

Additionally, the "new", Db2 12 TRANSFER OWNERSHIP command is implemented as a simple, immediate change.

[1] Not all types of tables can be renamed. Consult the IBM Db2 SQL Reference manual, page 2163, for types of tables and options that forbid renaming a table.
[2] Adding a column at the end of a table requires that the column be nullable or have a default assigned, otherwise it is a complex change
[3] Can change data type within data type families (text to text, number to number, etc.)
[4] Can change length as an immediate change as long as it is larger, otherwise it is a complex change.
[5] With the caveat that the CHECK utility will have to be run to enforce a check constraint if the CURRENT RULES ‘DB2’ option is in effect
[6] When a materialized query table is dropped, all packages dependent on it are invalidated

Tuesday, April 14, 2020

Db2 for z/OS and Managing Database Changes - Part 1

Today we begin a multi-part series of blog posts taking a look at what is involved in making database changes in a Db2 for z/OS environment. The first thing that DBAs will need is the ability to change all the database objects supported by Db2 for z/OS. There are numerous different types of  database objects and structures that can be created and modified by DDL, and at one point or another, DBAs are called upon to create, alter, and drop every one of them.
But let’s dig a little deeper into what is required. Assume that you are a Db2 DBA who has been given a request to make several changes to database structures. The first thing you must do, of course, is to review the requested changes to make sure they are appropriate. Assuming they are, what is the next step?

You must determine how to go about making each change. At a high level, there are three different types of schema changes: 
  • simple (or immediate), 
  • medium (or pending), and 
  • complex. 

Simple changes can be implemented immediately without requiring intervening actions. Medium changes require a bit more work to implement by running a REORG, and then we have complex changes that require an in-depth script for dropping and re-creating the database object. But not every type of database change request can use each type of schema change method. There are requirements and nuances in deciding which method can be used when.

In our next blog post, we will discuss simple Db2 changes.

Friday, April 10, 2020

IBM Db2 Analytics Accelerator: Time to Upgrade?

This post is about the IBM Db2 Analytics Accelerator, sometimes (and hereinafter) referred to as IDAA.
First of all, for those who don’t know, let’s start with what it is. IDAA is a high-performance component, typically delivered as an appliance, that is tightly integrated with Db2 for z/OS. It delivers high-speed processing for complex Db2 queries to support business-critical reporting and analytic workloads.  

The general idea is to enable HTAP (Hybrid Transaction Analytical Processing) from the same database, on Db2 for z/OS. IDAA stores data in a columnar format that is ideal for speeding up complex queries – sometimes by orders of magnitude.

Now there is a lot more to IDAA, but we won’t cover it here in today’s blog. If you want more details, I direct you to the following links:

Anyway, the real purpose of today’s blog entry is to alert IDAA users that you need to be aware of some recent and upcoming support and version issues.

IDAA Version 7

The current version of IDAA is V7.5; it was announced October 15, 2019 and released for GA December 6, 2019. But many customers are not there yet. This is not surprising given that it has only been about 4 or 5 months since it has become available. Nevertheless, it offers an abundance of great functionality and usability improvements. At the top of the list are greater scalability and improved synchronization.

Because the data in an IDAA is stored separately from the data in the primary Db2 for z/OS system, when the data is changed in Db2 for z/OS it must be migrated to the IDAA. This causes latency, where the data differs between the two systems. Of course, this is not ideal.

Well, the latest and greatest iteration of IDAA has greatly improved things with Integrated Synchronization, which provides low-latency data coherency. Db2 12 for z/OS (FL 500) delivers the Log Data Provider, which to capture changes and funnel them to IDAA. It is quick, uses very little CPU, and is zIIP-enabled. This greatly improves the latency between Db2 for z/OS data and IDAA data, to the point of it becoming mostly irrelevant.

Additionally, V7 was the first version of IDAA to allow deployment on IFLs, instead of on a separate physical piece of hardware. This means you can accelerate Db2 for z/OS queries completely on the mainframe. And V7.5 expands the scalability of IFLs.

Important Information for Laggards

Perhaps the most important piece of information in today’s blog post though is for those of you who are still running older versions of IDAA… specifically, V4. The end of service date for IDAA V4 is imminent – April 30, 2020 – and there will be no extension of this date. So if you are still on V4, it is time to upgrade!

Fortunately, you can upgrade to IDAA V5 at no cost. Sure, V5 is not the most current version of IDAA, but IBM has not issued an end of service (EOS) date for it yet. The probable EOS date is tentatively set for the first half of 2023 (which is the same for the IBM PureData System for Analytics N3001 on which this earlier IDAA is based.

Today’s Bottom IDAA Line

If you are looking for an efficient, cost-effective query accelerator for your complex Db2 queries you should look into IDAA V7.5.

And if you are still running V4, update soon (by the end of the month?) to avoid running on an out of service version of IDAA.

Monday, April 06, 2020

Db2 Quarantine Book Sale

Just a quick note to offer up a discount on my latest book, A Guide to Db2 Performance for Application Developers, during the quarantine. The book was written for application programmers, providing guidance and assistance for writing efficient application code for Db2. The book covers both Db2 for z/OS and Db2 for LUW, and is available in both printed and eBook formats:

So how do you get a discount? 
Then you will need to decide if you want the ebook or the print book, and when checking out, enter the correct coupon code. 
  • For the print book, use code db2N for 10% off
  • For the ebook, use code db2W for 5% off

Then enter your payment details and enjoy!

This book will make you a better programmer by teaching you how to write efficient code to access Db2 databases. Whether you write applications on the mainframe or distributed systems, this book will teach you practices, methods, and techniques for optimizing your SQL and applications as you build them. Write efficient applications and become your DBA's favorite developer by learning the techniques outlined in this book!

What you will get from reading this book is a well-grounded basis for designing and developing efficient Db2 applications that perform well.

If you'd rather order the book somewhere else (without the discounts) it is also available at:
But I hope you'll order a copy today for yourself, your favorite programmer, or better yet, your least-favorite programmer (because the book will help improve their abilities)!

Thursday, April 02, 2020

A Condensed 35-Year History of DB2 for z/OS (...and Db2 for z/OS)

Let's go back in time... over three decades ago... back to the wild and woolly 1980s! And watch our favorite DBMS, DB2, grow up over time.

DB2 Version 1 Release 1 was announced on June 7, 1983, and it became generally available on Tuesday, April 2, 1985. I wonder if it was ready on April 1st but not released because of April Fool’s Day? Initial DB2 development focused on the basics of making a relational DBMS work. Early releases of DB2 were viewed by many as an “information center” DBMS, not for production workloads, like IMS was.

Version 1 Release 2 was announced on February 4, 1986 and was released for general availability a month later on March 7, 1986. Can you imagine waiting only a month for a new release of DB2 these days? But that is how it happened back then. Same thing for Version 1 Release 3, which was announced on May 19, 1987 and became GA on June 26, 1987. DB2 V1R3 saw the introduction of DATE data types.

You might notice that IBM delivered “releases” of DB2 back in the 1980s, whereas today (and ever since V3) there have only been versions. Versions are major changes, whereas releases are not quite as significant as a version.

Version 2 Release 1 was announced in April 1988 and delivered in September 1988. Here we start to see the gap widening again between announcement and delivery. V2R1 was a significant release in the history of DB2, a bellwether of sorts for when DB2 began to be viewed as capable of supporting mission-critical, transaction processing workloads. Not only did V2R1 provide significant performance enhancements but it also signaled the introduction of declarative Referential Integrity (RI) constraints.

No sooner than V2R1 became GA than IBM announced Version 2 Release 2 on October 4, 1988. But it was not until a year later that it became generally available on September 23, 1988. DB2 V2R2 again bolstered performance in many ways. It also saw the introduction of distributed database support (private protocol) across MVS systems.

Version 2 Release 3 was announced on September 5, 1990, and became generally available on October 25, 1991. Two very significant features were added in V2R3: segmented table spaces and packages. Segmented table spaces quickly became a de facto standard and packages made DB2 application programs easier to support. DB2 V2R3 is also the version that beefed up distributed support with Distributed Relational Database Architecture (DRDA).

Along comes DB2 Version 3, announced in November 1993 and GA in December 1993. Now it may look like things sped up again here, but not really. This is when the early support program for DB2 started. Early support was announced in March 1993 and delivered to customers in June 1993. V3 greatly expanded the number of buffer pool options available (from 5 pools to 80), and many advances were made for DB2 to take better advantage of the System 390 environment, including support for hardware-assisted compression and hiperpools. It was also V3 that introduced I/O parallelism for the first time.

Version 4 signaled another 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. Data Sharing made its debut in V4, too, and with it, DB2 achieved new heights of scalability and availability allowing users to upgrade without an outage and to add new subsystems to a group “on the fly.” DB2 V4 also introduced stored procedures, as well as CP parallelism.

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, that 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 became 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, network computing, performance and availability, capacity improvements, data sharing enhancements, and 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.

DB2 Version 8 followed, but not immediately. IBM took advantage of Y2K and the general desire of shops 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!

With DB2 9 for z/OS, we drop the “V” from the name. Is that in response to Oracle’s naming conventions? Well, we do add a space between the DB2 and the version number because we don’t want to talk about DB-twenty-nine! A lot of great new functionality comes with DB2 9 including additional database definition on demand capabilities, binary data types, and a lot of new SQL capabilities including OLAP functions and EXCEPT/INTERSECT. But probably the biggest new feature is pureXML, which allows you to store DB2 data as native XML. The XML is stored natively as a new data type that can be searched and analyzed without the need to reformat it. The approach was novel in that it  supports native XML, basically enabling dual storage engines.

And that brings us to DB2 10 for z/OS. This version of DB2 was built to take advantage of many zEnterprise (the latest new mainframe at the time) features to deliver scalability. Examples include improved compression, cache optimization, blades for running the Smart Analytics Optimizer, etc. 

Additional capabilities included many performance improvements (BIND, IN-list, utilities, etc.), hash organized table spaces, high-performance DBATs (DDF threads) forced to use RELEASE COMMIT, parallel index updating, efficient caching of dynamic SQL with literals, temporal data support, safe query optimization, improved access path hints, access to currently committed data, new TIMESTAMP precision and time zones, and buffer pool options for pinning objects in memory.

In October 2013 we got another new version, DB2 11 for z/OS. Click on that link if you want all the details, but some highlights included transparent archiving, global variables, improved SQL PL, APREUSE(WARN), significant utility improvements, DROP COLUMN support, and JSON support with IBM BigInsights.

And that brings us to the present day, with DB2 12 for z/OS as the current (and soon to be only) supported version of Db2. Released for general availability in October 2016, DB2 12 for z/OS abandons the traditional new release cycle that IBM has followed for decades, adopting a new continuous delivery model. New functionality is now delivered in Function Levels (FLs) that are easily applied and delivered much more rapidly than in the past. Indeed, the current Db2 function level is FL506, which means there have been 6 new function levels added since 2016.

Version 12 brought with it a plethora of new capabilities including virtual storage enhancements, optimization improvements, and improved control over the introduction of new SQL capabilities. DB2 12 for z/OS delivered many improvements for both application development and database administration. Examples of new application capabilities include:
  • Additional support for triggers, arrays, global variables, pureXML, and JSON
  • MERGE statement enhancements
  • SQL pagination support
  • Support for Unicode columns in an EBCDIC table
  • Piece-wise deletion of data
  • Support for temporal referential constraint
  • More flexibility in defining application periods for temporal tables
  • PERCENTILE function support
  • Resource limits for static SQL statements
  • Db2 REST services improve efficiency and security
  • DevOps with Db2: Automated deployment of applications with IBM UrbanCode Deploy
Examples of new DBA and SYSADM capabilities include:

  • Installation or migration without requiring SYSADM
  • Improved availability when altering index compression
  • Online schema enhancements
  • Improved catalog availability
  • Object ownership transfer
  • Improved data validation after running DSN1COPY
  • Automatic start of profiles at Db2 start
  • Increased partition sizes and simplified partition management for partition-by-range table spaces with relative page numbering
  • Ability to add partitions between existing logical partitions
  • UNLOAD privilege for the UNLOAD utility
  • Temporal versioning for Db2 catalog tables
  • Statistics collection enhancements for SQL performance    
Of course, these are just some of the V12 improvements; there are many more (as well as all of the Function Level improvements)!

Then sometime in the middle of 2017, IBM decided to change the name of DB2 by making the uppercase B a lowercase b. So now the name of our beloved DBMS is Db2. Nobody has been able to explain to me what the benefit of this was, so don’t ask me!

The Bottom Line

I worked with DB2 way back in its Version 1 days, and I’ve enjoyed watching DB2 grow over its first 35 years. Of course, we did not cover every new feature and capability of each version and release, only the highlights. Perhaps this journey back through time will help you to remember when you jumped on board with Db2 and relational database technology. I am happy to have been associated with Db2 (and DB2) for its first 35 years and I look forward to many more years of working with Db2…