Tue, Apr
0 New Articles

RPG Academy: Database Modernization - Methodology, Part 3

  • Smaller Small Medium Big Bigger
  • Default Helvetica Segoe Georgia Times

It’s time to get your hands dirty and actually begin the database modernization process. Learn how to start and manage the physical-file-to-table conversion process in this TechTip.

The previous two TechTips discussed the organizational aspects of the database modernization process. It’s now time to start converting your old-school, DDS-defined physical files to “modern” and better-performing DDL tables.

Converting DDS to DDL

Some tools, like AO Foundation (which I mentioned a couple of TechTips back) enable you to automate the task of converting DDS to DDL. However, you can (and, in my opinion, should) know how to convert the files manually. It’s actually a simple process:

  1. Open IBM i Navigator.
  2. Go to the Databases node in the left section of the screen and select your database.
  3. Select Schemas and choose the library where the file resides.
  4. Find the file you want to convert, right-click it, and choose Generate SQL.

The Run SQL Scripts tool will pop up, and show you a CREATE TABLE or CREATE VIEW statement, depending on the type of file you selected. This statement should be a fairly accurate approximation of the DDS defined file. In most cases, it will be an exact match. However, because some DDS keywords don’t have an SQL equivalent, you might not always get what you want. Table 1 lists these keywords.

Table 1: DDS Keywords Ignored During SQL Generation

File Type


Both Physical and Logical Files


Logical Files


Join Logical Files


Keep in mind that, depending of the IBM i Access software version that you’re using, these steps may vary a little. Once you find and run the Generate SQL option, carefully review the results, and adjust as necessary. Some situations might require changes in your programs, while for others you might find an “SQL way” of solving the problem. Before you run the statement and generate the SQL object, be sure to change the library name. You might want to change the SQL object name to something longer and more descriptive, as discussed in the previous TechTip. Keep in mind that you need to maintain compatibility with the programs that use the “old” file.

If the DDS object to convert is a physical file, there are a few additional tasks to perform. If you’re not familiar with the CREATE TABLE SQL statement syntax, it might be a good idea to review it at this time. Also, because SQL is not constrained by the operating system 10-character limit, consider using longer, more descriptive names for each column, followed by the FOR COLUMN expression, after which you’ll place the DDS name of the column. Finally, add the RCDFMT keyword with the DDS record format name to ensure your RPG programs are still able to use the table/file as they did before.

Logical files present different challenges. If the logical file you’re converting has a key, you’ll need to create an SQL index with that key and create a view with the selected columns. There are some limitations to this process, however. Multi-member files cannot be converted directly, for instance, because SQL can’t handle them. You’ll need multiple tables to store the information. If you want to convert such a file, you need to get creative and figure out a way to migrate the data from the original physical file to new SQL tables and, for example, create a stored procedure that automatically accesses the right one.

Finally, you can select a file name and location to save the SQL script. Always remember to save scripts before running them, because sometimes the execution ends in errors or freezes, and you might lose unsaved work. Try this for a couple of physical files and their dependent logical file. Ideally, choose files that are not used in many programs and do a proof of concept (PoC), just to get the hang of it and start hammering out possible inconsistencies in your process. Note that this is a high-level description of the whole DDS-to-DDL conversion process. To get a more technical-level description, please refer to the vast literature on this topic and, naturally, the experience and guidance of your modernization consultant.

Once you’re happy with the conversion and have performed all the necessary program adjustments and recompilations, you’ll be ready to move to the next stage. By now, you should notice an interesting performance gain. This results, among other things, from the larger page size of SQL indexes (64 Kb) compared to the native access paths (8 Kb) used by logical files.

Here’s where things start to get really interesting. You’re now ready to squeeze some more performance from your database and modernize it at the same time. This should be enough to keep you busy until the next TechTip of this series, which will be about the second step of “tidying up” your database: normalization.

Coming Up

In the first article of this Database Modernization subseries, I explained the theory behind the whole normalization theory. Next time around, I’ll show you how to methodically approach the subject. Until then, comment, correct, or suggest a topic in the Comments section below.

Rafael Victoria-Pereira

Rafael Victória-Pereira has more than 20 years of IBM i experience as a programmer, analyst, and manager. Over that period, he has been an active voice in the IBM i community, encouraging and helping programmers transition to ILE and free-format RPG. Rafael has written more than 100 technical articles about topics ranging from interfaces (the topic for his first book, Flexible Input, Dazzling Output with IBM i) to modern RPG and SQL in his popular RPG Academy and SQL 101 series on mcpressonline.com and in his books Evolve Your RPG Coding and SQL for IBM i: A Database Modernization Guide. Rafael writes in an easy-to-read, practical style that is highly popular with his audience of IBM technology professionals.

Rafael is the Deputy IT Director - Infrastructures and Services at the Luis Simões Group in Portugal. His areas of expertise include programming in the IBM i native languages (RPG, CL, and DB2 SQL) and in "modern" programming languages, such as Java, C#, and Python, as well as project management and consultancy.

MC Press books written by Rafael Victória-Pereira available now on the MC Press Bookstore.

Evolve Your RPG Coding: Move from OPM to ILE...and Beyond Evolve Your RPG Coding: Move from OPM to ILE...and Beyond
Transition to modern RPG programming with this step-by-step guide through ILE and free-format RPG, SQL, and modernization techniques.
List Price $79.95

Now On Sale

Flexible Input, Dazzling Output with IBM i Flexible Input, Dazzling Output with IBM i
Uncover easier, more flexible ways to get data into your system, plus some methods for exporting and presenting the vital business data it contains.
List Price $79.95

Now On Sale

SQL for IBM i: A Database Modernization Guide SQL for IBM i: A Database Modernization Guide
Learn how to use SQL’s capabilities to modernize and enhance your IBM i database.
List Price $79.95

Now On Sale



Support MC Press Online

$0.00 Raised:

Book Reviews

Resource Center

  • SB Profound WC 5536 Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application. You can find Part 1 here. In Part 2 of our free Node.js Webinar Series, Brian May teaches you the different tooling options available for writing code, debugging, and using Git for version control. Brian will briefly discuss the different tools available, and demonstrate his preferred setup for Node development on IBM i or any platform. Attend this webinar to learn:

  • SB Profound WP 5539More than ever, there is a demand for IT to deliver innovation. Your IBM i has been an essential part of your business operations for years. However, your organization may struggle to maintain the current system and implement new projects. The thousands of customers we've worked with and surveyed state that expectations regarding the digital footprint and vision of the company are not aligned with the current IT environment.

  • SB HelpSystems ROBOT Generic IBM announced the E1080 servers using the latest Power10 processor in September 2021. The most powerful processor from IBM to date, Power10 is designed to handle the demands of doing business in today’s high-tech atmosphere, including running cloud applications, supporting big data, and managing AI workloads. But what does Power10 mean for your data center? In this recorded webinar, IBMers Dan Sundt and Dylan Boday join IBM Power Champion Tom Huntington for a discussion on why Power10 technology is the right strategic investment if you run IBM i, AIX, or Linux. In this action-packed hour, Tom will share trends from the IBM i and AIX user communities while Dan and Dylan dive into the tech specs for key hardware, including:

  • Magic MarkTRY the one package that solves all your document design and printing challenges on all your platforms. Produce bar code labels, electronic forms, ad hoc reports, and RFID tags – without programming! MarkMagic is the only document design and print solution that combines report writing, WYSIWYG label and forms design, and conditional printing in one integrated product. Make sure your data survives when catastrophe hits. Request your trial now!  Request Now.

  • SB HelpSystems ROBOT GenericForms of ransomware has been around for over 30 years, and with more and more organizations suffering attacks each year, it continues to endure. What has made ransomware such a durable threat and what is the best way to combat it? In order to prevent ransomware, organizations must first understand how it works.

  • SB HelpSystems ROBOT GenericIT security is a top priority for businesses around the world, but most IBM i pros don’t know where to begin—and most cybersecurity experts don’t know IBM i. In this session, Robin Tatam explores the business impact of lax IBM i security, the top vulnerabilities putting IBM i at risk, and the steps you can take to protect your organization. If you’re looking to avoid unexpected downtime or corrupted data, you don’t want to miss this session.

  • SB HelpSystems ROBOT GenericCan you trust all of your users all of the time? A typical end user receives 16 malicious emails each month, but only 17 percent of these phishing campaigns are reported to IT. Once an attack is underway, most organizations won’t discover the breach until six months later. A staggering amount of damage can occur in that time. Despite these risks, 93 percent of organizations are leaving their IBM i systems vulnerable to cybercrime. In this on-demand webinar, IBM i security experts Robin Tatam and Sandi Moore will reveal:

  • FORTRA Disaster protection is vital to every business. Yet, it often consists of patched together procedures that are prone to error. From automatic backups to data encryption to media management, Robot automates the routine (yet often complex) tasks of iSeries backup and recovery, saving you time and money and making the process safer and more reliable. Automate your backups with the Robot Backup and Recovery Solution. Key features include:

  • FORTRAManaging messages on your IBM i can be more than a full-time job if you have to do it manually. Messages need a response and resources must be monitored—often over multiple systems and across platforms. How can you be sure you won’t miss important system events? Automate your message center with the Robot Message Management Solution. Key features include:

  • FORTRAThe thought of printing, distributing, and storing iSeries reports manually may reduce you to tears. Paper and labor costs associated with report generation can spiral out of control. Mountains of paper threaten to swamp your files. Robot automates report bursting, distribution, bundling, and archiving, and offers secure, selective online report viewing. Manage your reports with the Robot Report Management Solution. Key features include:

  • FORTRAFor over 30 years, Robot has been a leader in systems management for IBM i. With batch job creation and scheduling at its core, the Robot Job Scheduling Solution reduces the opportunity for human error and helps you maintain service levels, automating even the biggest, most complex runbooks. Manage your job schedule with the Robot Job Scheduling Solution. Key features include:

  • LANSA Business users want new applications now. Market and regulatory pressures require faster application updates and delivery into production. Your IBM i developers may be approaching retirement, and you see no sure way to fill their positions with experienced developers. In addition, you may be caught between maintaining your existing applications and the uncertainty of moving to something new.

  • LANSAWhen it comes to creating your business applications, there are hundreds of coding platforms and programming languages to choose from. These options range from very complex traditional programming languages to Low-Code platforms where sometimes no traditional coding experience is needed. Download our whitepaper, The Power of Writing Code in a Low-Code Solution, and:

  • LANSASupply Chain is becoming increasingly complex and unpredictable. From raw materials for manufacturing to food supply chains, the journey from source to production to delivery to consumers is marred with inefficiencies, manual processes, shortages, recalls, counterfeits, and scandals. In this webinar, we discuss how:

  • The MC Resource Centers bring you the widest selection of white papers, trial software, and on-demand webcasts for you to choose from. >> Review the list of White Papers, Trial Software or On-Demand Webcast at the MC Press Resource Center. >> Add the items to yru Cart and complet he checkout process and submit

  • Profound Logic Have you been wondering about Node.js? Our free Node.js Webinar Series takes you from total beginner to creating a fully-functional IBM i Node.js business application.

  • SB Profound WC 5536Join us for this hour-long webcast that will explore:

  • Fortra IT managers hoping to find new IBM i talent are discovering that the pool of experienced RPG programmers and operators or administrators with intimate knowledge of the operating system and the applications that run on it is small. This begs the question: How will you manage the platform that supports such a big part of your business? This guide offers strategies and software suggestions to help you plan IT staffing and resources and smooth the transition after your AS/400 talent retires. Read on to learn: