DB2 -- What's in a Name?

Versions of DB2 exist for a large array of platforms, of which the mainframe (z/OS) is only one. Of course, it is my favorite one since I’ve been working on mainframe technology now for decades and have worked with DB2 since Version 1.

It used to be easy: DB2 meant IBM’s mainframe SQL database management system based on the relational model. But you can’t just say the term “DB2” any more and expect people to understand what you mean.

Today there are variations of DB2 that run on the iSeries (AS/400), on Linux, Unix, and Windows (LUW) platforms, and even one that runs on PDAs and smart phones called DB2 Everyplace. Not to mention the mainframe variations that run on z/OS, VM, and VSE.
These products are all collectively referred to by IBM as the DB2 Family. Individually, each DBMS is referred to as DB2, or sometimes DB2 Universal Database Server. There was a period of time when DB2 for LUW was called UDB and DB2 for z/OS was just called DB2. Then IBM tried to rebrand both as DB2 UDB. But that seems to have gone away several versions ago now.
The proper way to refer to any individual offering in the DB2 family is DB2 for (operating system) (for example, DB2 for z/OS or DB2 for Windows).

Different Code Bases

There are four distinct code bases for the products under the DB2 brand. The mainframe has its own code base, as does the iSeries, and VSE/VM. The fourth code base is for Linux, Unix, and Windows (LUW) platforms—and the other DB2 offerings (e.g. DB2 Everyplace) originate from this code base.

Having a separate code base means that each of these DB2 “products” was developed independently from the others. So, for example, the process used by DB2 for z/OS to optimize SQL differs from the process used by DB2 for Linux. Usually, though, the result is similar—an efficient SQL statement.

But keep in mind that there will be some differences between the DB2s.

Some of the Differences

It is obvious that the different DB2 products are not “plug and play” commodities simply because they all share the name DB2. There are some big differences among these products in their current releases. The biggest differences are relatively easy to detect and include the following:

• Differences imposed due to operating system constraints
  (OS/400 versus z/OS versus AIX)
• Back-level compatibility issues
• Workstation orientation differences such as GUI interfaces and drag-and-drop menus
• Subsystem-centric implementation (z/OS) versus database-centric implementation (workstation)

Most of these differences are minor and easy to handle. Indeed, IBM has slowly but surely been making these disparate implementations of DB2 more and more alike with each new release and version. The interface (or API) by which most people access any of the DB2 Family is SQL and there is broad compatibility among the SQL implementations of the members of the DB2 Family (though not 100 percent, of course).

A misconception “out there” in DB2-land is that the LUW platform drives new features, but a review of the changes that have been introduced to DB2 over the past several versions and releases does not bear that out. Some features are introduced on the mainframe first; others on the distributed platforms first.

Of the basic differences mentioned earlier, the only one that might not be obvious is the focus of the DBMS implementation. DB2 for LUW is database-centric. This implies that each new database carries its own system catalog with it. Additionally, it is not possible to simply access tables across different databases; distributed access is required.

On z/OS, DB2 is subsystem-centric. A single system catalog spans databases. Each subsystem has a unique identification, and you can create multiple databases within it. Distributed requests are not required to access databases within the same subsystem (or, indeed, across multiple subsystems in a data-sharing environment).

Another concept that is different at the workstation level is that of a directory. The DB2 for z/OS Directory houses DBMS system-related information regarding DBD structure, skeleton plan and skeleton package tables, RBA log ranges, and utility control data. The information cannot be updated by the user but is managed and controlled by DB2.

At the workstation level, a directory is another matter altogether. For example, the directory structure used by DB2 for LUW controls the overall environment.

• The System Database Directory identifies the databases that can be accessed from the workstation and contains an entry for each local and remote one. Each database entry contains the database name, alias, entry type, and location.
• One Volume Database Directory is allocated per disk drive that contains a workstation database. Each entry identifies the location of a specific database on the drive.
• The Workstation Directory is used to make a connection to a remote database server. It is used in conjunction with the Database Connection Services Directory to make a connection to a remote host server.
• The Database Connection Services Directory is used by DB2 Connect to make a connection to a remote host server.

Not only is it possible for the user to update these directories, it is required. The workstation directories define the environment of DB2 for LUW. Without the proper information recorded in these directories, DB2 might not function in the desired manner. The information in these directories is somewhat analogous to DB2 for z/OS DSNZPARMs and the SYSDDF system catalog tables.

Database Structures

Not all the objects available to DB2 for z/OS users are supported at the workstation level. For example, hardware-specific DB2 objects such as table spaces and storage groups are not available for DB2 on other platforms, at least not in the same way that mainframers are used to dealing with them. Partitioning and segmenting as it is done on z/OS is not done on other platforms.

However, DB2 for LUW does provide a feature known as a segmented table. But this is not the same concept as a DB2 for z/OS segmented table space. DB2 for LUW segmented tables are used to span volumes, enabling DB2 to get around file size limitations.

The file structure used for databases differs from platform to platform. For example, DB2 for z/OS uses VSAM Linear Data Sets (LDS) or Entry Sequenced Data Sets (ESDS). A database deployed on DB2 for LUW uses two files for table data: one for normal data and a second to store long fields. These workstation files are flat files, not VSAM files.

Although tables are basically the same for all of the DB2 environments, not all of the DDL options are provided in all of the environments.

Optimizer Differences

One of the most significant benefits of relational databases is that they provide built-in optimization. The DB2 for z/OS optimizer is well-known to mainframe DB2 users, but how similar are the other DB2 optimizers?

DB2 for LUW uses the latest and greatest optimization technology from IBM -- the Starburst optimizer (which arose from IBM’s Almaden research lab). Starburst is a database optimization research project that has been covered quite extensively in the academic press.

As one example of the difference, consider that the DB2 for LUW optimizer has varying levels of optimization that can be selected by the user. This concept is not implemented in DB2 for z/OS.

Although some Starburst technology will find its way to DB2 for z/OS, the mainframe DB2 optimizer will not be completely replaced by Starburst technology. Doing so would not be wise because the DB2 for z/OS optimizer has been finely tuned for its environment over the course of almost three decades.

Another interesting tidbit is that DB2 for iSeries provides an access method for programmers in which they can bypass the relational engine. This is not encouraged, but it is available.

Other Differences

Other differences exist between the different implementations of DB2. Some of these are caused by the different release cycles IBM has created for the differing platforms. The bottom line is that you need to be aware that there are differences between the DB2s on different platforms. Whenever you use a specific implementation of DB2, you need to be aware of the features it supports that other DB2 platforms do not, as well as the features it does not support that other DB2 platforms do support.

Packaging and Naming Issues

The actual name of the DB2 edition can be tricky to master on non-mainframe platforms. On the mainframe you just say “I want DB2,” and that is what you get. Well, almost. You also have to decide whether you want IBM’s utilities or not, too.

But things are more difficult in the LUW world. The following packages are all available for DB2 on Linux, Unix, and Windows:

DB2 Workgroup Server Edition (WSE) is a multi-user, single host, DBMS at the departmental user. It should be deployed for smaller systems with a limited number of users.

DB2 Enterprise Server Edition (ESE) is the highest level of DB2 database version with intra-partition parallelism support (the database engine can process SQL statement segments in parallel), and inter-partition parallelism support (process a query in parallel across all of the nodes). ESE has Partitioning and Clustering options as additional add-on features. So, this is the enterprise DB2.

DB2 Advanced Enterprise Server Edition (AESE) sounds like a step up from ESE, and it is, kind of... but not really in terms of key DBMS technology. The advanced means that IBM integrates Optim and InfoSphere technologies into the product.

DB2 Express Edition is targeted at entry level users at a low price point. Small shops, partners, and new users can build applications on top of DB2 Express.

And DB2 Express-C is IBM’s “free” DBMS offering providing all the “core” capabilities of DB2 at no charge. So why use an open source DBMS when you can get a free version of DB2?
A handy comparison of the editions is available on IBM’s web site.

Summary

So you see, saying DB2 is no enough any more. Which DB2? They’re all great, but it can take some time to wrap your arms around all of this…

DB2 Symposium 2011

Today's blog post is about a great symposium dedicated to the topic of DB2. It is called, appropriately enough, the DB2 Symposium. DB2 Symposium is a three day training event with one day seminars presented by well-known DB2 consultants. I was fortunate enough to be asked to participate this year by the primary organizer of the event, Klaas Brant. For those of you who don't know him, Klaas is a well-respected DB2 consultant based in the Netherlands... and an all around great guy.

Why should I attend the DB2 Symposium you may ask? Don't IDUG and IOD provide everything I need in the way of events? Well, DB2 Symposium fills the gap between a conference and a multi-day training course. The DB2 Symposium is unique because you can participate for 1, 2, or 3 days, depending on your needs and budget.

Although it has not been to the USA the past few years, the DB2 Symposium is a regular, well-known event in Europe! And after a period of absence the DB2 Symposium is back in the USA.

The USA DB2 Symposium is happening soon, so you'll need to act fast if you want to participate. It occurs March 21-23, 2011 in the Dallas, Texas area. More precisely, at the Hilton Arlington (2401 East Lamar Boulevard, Arlington, Texas, USA 76006-7503). Each day the training sessions start at 9.00am and end at around 5.00pm.

But registration on site is not possible, you must pre-register online... so plan ahead!

My session is on March 21st and it is called DB2 Developer's Guide Comes Alive! This one day session, covers tips, techniques, and procedures you need to know in order to excel at administering and using DB2 on the mainframe.The material is based upon DB2 Developer's Guide, the best-selling DB2 for z/OS book on the market. Additionally, the course material will contain references to sections of the book for students to find additional material on each topic after the sessions. Topics to be covered will include:

• A performance tuning roadmap for managing DB2 application, database and system performance. You will learn SQL coding and tuning techniques, guidance for database optimization and reorganization, coverage of buffer pool settings and parameters for performance.
• Logical and physical database design recommendations for DB2, so you can build and maintain effective DB2 databases immediately. Includes discussion of standards, logical to physical translation, data types, usage of nulls, and more.
• Information and guidance on BINDing and REBINDing, along with a discussion of the most important parameters.
• Along the way we'll look at locking, access paths, statistics, indexing and more.
• And even though the current edition of the book covers through DB2 V8, this course adds coverage of some of the newer features added to DB2 in versions 9 and 10 that can boost your productivity and performance.

If you own the book already, bring it along and I'll be happy to autograph it for you. And then you can use it along with the course materials... and if you don't own it already, you'll probably want to grab a copy after attending the seminar... you can always find a link to buy my books on the front page of my web site at http://www.craigsmullins.com.

So register for the DB2 Symposium today... and I'll see you in Dallas, pardner!

A Video from IOD, DB2 -- Monday 10/25

This video was shot by Rebecca Bond at the IBM Information On Demand Conference 2010 in Las Vegas. She was interviewing DB2 folks on what they do and the benefit they get from attending IOD. I am the third interview... but don't just skip to me! Listen to Melanie and Fred, too!

News From The IOD Conference

As usual, IBM has put out a number of press releases in conjunction with the Information On Demand conference, and I will use today’s blog to summarize some of the highlights of these releases.

First of all, IBM is rightly proud of the fact that more than 700 SAP clients have turned to IBM DB2 database software to manage heavy database workloads for improved performance… and, according to IBM, at a lower cost. By that they mean at a lower cost than Oracle. Even though the press release does not state that these SAP sites chose DB2 over Oracle, the IBM executive I spoke with yesterday made it clear that that was indeed the case.

This stampede of SAP customers over to DB2 should not be a surprise because DB2 is SAP’s preferred database software. This might be surprising given that SAP recently acquired Sybase, but IBM notes that seven Sybase runs SAP on DB2.

The press release goes on to call out several customers who are using DB2 with SAP and their reasons for doing so. For example, Reliance Life chose DB2 for the better transaction performance and faster access to data it delivered. Banco de Brasil, on the other hand, was looking to reduce power consumption and storage by consolidating its database management systems.

IBM also announced new software that helps clients automate content-centric processes and manage unstructured content. The highlight of this announcement is IBM Case Manager, software that integrates content and process management with advanced analytics, business rules, collaboration and social software.

IBM also enhanced its content analytics software. NTT DOCOMO of Japan is impressed with IBM’s offering. “With Content Analytics, we have an integrated view of all information that’s relevant to out business in one place regardless of where it’s stored,” said Makoto Ichise, Manager of Information Systems Department Group at NTT DOCOMO.

IBM also enhanced its Information Governance solutions and announced further usage of it InfoSphere Streams product for analyzing medical data to improve healthcare.

So IBM software keeps improving and helping us to better manage our data in a constantly changing world…

Nominate Someone for the CA IDUG Award for Outstanding Work in DB2

As many of you know, each year CA sponsors an award at IDUG to honor outstanding work with DB2. The only requirement for the award is that you and your company have used DB2, either on the mainframe or distributed system, in a novel, ground-breaking, or cutting-edge manner.

There is no requirement that an entrant organization be based in North America. There is also no requirement that an entrant organization license or use specific CA or other vendor database management tools or that he/she attend the IDUG conference in person. All nominations will be judged by a panel of independent DB2 consultants in conjunction with CA executives.

Nominations are now open through April 26, 2010. To learn more, visit ca.com/awards/db2.

The winner will be announced at the IDUG North America conference, May 10-14, 2010.

Each winner will receive:

• One complimentary full IDUG conference pass for any IDUG Europe or IDUG North America conference held prior to December 2011
  
• Half-day consulting engagements by each of the consultant judges within 12 months of award presentation
  
• Expense reimbursement up to $1,500 either (a) the winner’s travel to an IDUG conference held prior to December 2011 or (b) travel by one of the DB2 consultants for on-site provision of the complimentary consulting services described above
  
• Recognition plaque
  

Submit your project today and get recognized for your outstanding work. Visit ca.com/awards/db2.

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Quick Thoughts on DB2 Performance

Database performance problems are not caused by magic. Indeed, all performance problems are always caused by change. That statement flies in the face of what I normally say, which is “Almost never say always or never”… but in this case, it is true.

Think about it for a moment. If everything remains stable and unchanging in your environment, then why would performance vary? That’s right, it wouldn’t.

Something tangible must change before a performance problem can be experienced. The challenge of performance tuning is to find the source of the change, gauge its impact, and formulate a solution.

Change can take many forms, including the following:

• Physical changes to the environment, such as a new CPU, new disk devices, or different tape drives.
  
• Changes to system software, such as a new release of a product (for example, WebSphere, CICS, or even z/OS), the alteration of a product (for example, the addition of more or fewer CICS regions or an IMS SYSGEN), or a new product (for example, implementation of DFHSM). Also included is the installation of a new release or version of DB2, which can result in changes in access paths as well as utilization of new features.
  
• Changes to the DB2 engine from maintenance releases and PTFs, which can change the optimizer (and sometimes introduce other new functionality).
  
• Changes in system capacity. More or fewer jobs could be executing concurrently when the performance problem occurs. Or additional users may be banging away at your transactions.
  
• Environmental changes, such as the implementation of client/server programs, the adoption of SOA, or other new technologies.
  
• Database changes. This involves changes to any DB2 object, and ranges from adding a new column or an index to dropping and re-creating an object.
  
• Changes to the application development methodology, such as usage of check constraints instead of application logic or the use of stored procedures.
  
• Changes to application code, both SQL and host language code (COBOL, C, Java, etc.).
  

Although the majority of your performance problems are likely to be application-oriented, you must be prepared to explore any and all of these other areas when application tuning has little effect.

My advice is to be sure that you institute strict change control tracking across all areas of your IT infrastructure. That way, whenever you experience a performance problem, you will be able to track what has changed recently, along with who changed it and why. This is important because every DBA knows what the answer to the question “What changed?” will be… right?

It is always “nothing!”

And that cannot be true. Oh, it does not mean that the person answering is lying. He or she may not have changed anything. And it is not necessarily reasonable to expect an application developer to know what all could have changed…especially when what can impact DB2 performance spans so many areas of the IT infrastructure.

So do yourself… and your company a favor: be sure that you meticulously track each and every change to any aspect of your systems. Then – and this is where many shops break down – make sure that you have methods of tying all of the change information together in such a way that it can be queried and examined in the face of a performance problem.

Only then can you reasonably expect your DBAs rapidly to be able to track down and remedy DB2 performance problems… because only then will they have the pertinent information at their disposal.

Wordle of my DB2 Portal Blog

The "jumble" of words shown here is a Wordle, which is a "word cloud" of text. I fed my blog location into the Wordle generator and it created this pretty picture based on the words I most commonly use here in this blog.

The cloud gives greater prominence to words that appear more frequently in the source text. No surprise that "DB2" and "data" dominate the other words!

New DB2 Twitter List

Just a very quick post this morning to let all you DB2 Twitter folks out there know that I created a list of the DB2 tweeters I know about at http://twitter.com/craigmullins/db2-folks.

If you are a DB2 professional and I left you off the list please leave a comment here or drop me an e-mail and I'll be happy to add you.

Discount on IBM Information on Demand Conference

The IBM Information on Demand (IOD, for short) conference is rapidly approaching. The conference will be held in Las Vegas, Nevada the week of October 25 – 30, 2009 at the Mandalay Bay casino and hotel.

The IOD conference is IBM’s signature event for their data and information management product lines. By attending IOD 2009 you can gain unique perspectives from IBM experts, technical leaders and visionaries as well as peers in your industry. Many of the developers of IBM’s offerings, such as DB2, Informix, and IMS, will be delivering educational sessions at IOD. And over 200 customers will share real-world experiences detailing how they have unlocked the value of their information and realized tangible and immediate return on investment.

OK, so what about that discount? IBM has been kind enough to provide me with a discount code that I can share with my readers. You will need to provide the code, G09MULL, when your register for the conference and you will get a $100 discount off of your registration!

Here’s how to register on-line:

• Visit the IBM Information On Demand 2009 global conference website and select 'Register now' at: www.ibm.com/events/informationondemand

• An IBM userid and Password are required to register. If you have an existing IBM.com account ID, please select 'Register for the Conference' and sign on. If you do not have an IBM.com account ID, please follow the link 'MY IBM ID' to obtain one. Complete the form and click 'SUBMIT'. You will then be allowed to continue as a registered IBM user. Click 'Continue' and select 'Register for the Conference' and sign on with your new userid and password.

• Select registration type of 'Customer' and click 'Continue'

• Complete the appropriate fields on the enrollment form

• Under the 'Promotion Code Information' section, enter PROMOTION CODE G09MULL. You must enter this code to receive your $100 discount.

• Complete the form with attendee, arrival and payment information clicking 'Continue' at the bottom of each section.

• Click 'Submit Registration'

Note: Credit card information is required to guarantee your registration regardless of your method of payment and/or discount amount.

That’s all there is to it. And you can use the promotion code multiple times for all of the folks at you company that will be attending the Information On Demand conference in 2009.

Cheers!