26
Tue, Nov
1 New Articles

Practical RPG: BLOBs, CLOBs, and XML Part 1

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

The IFS is a great place to store stream files but it has some serious limitations. This series of articles presents an alternative.

 

Recently, several different requirements ended up colliding in a way that led me to do a lot of research on using Large Objects (LOBs) in my RPG programs. While they require a little bit of extra up-front investment, LOBs provide a way to integrate large-scale use of stream file data into your enterprise system.

Relating to LOBs

In the world of data processing (and I'm using that term very specifically), we see data in two very different ways: stream files and relational data. Most of us were familiar with relational data before we ever heard the term. That's especially true when using the larger umbrella definition of relational data that includes both standard indexed access data (what is called "native access" on the IBM i and ISAM, or indexed sequential access method to the rest of the computing world) and fully relational databases that support SQL access and all that entails, such as commitment control and database constraints.

 

Stream files, on the other hand, are the staple of both the PC and the UNIX world. Stream files derive their name from the fact that the data is usually processed in a stream, from beginning to end, rather than the random access of relational data. This is due to the fact that stream files have variable-length records; there's no easy way to position yourself to the beginning of the seventh line when each line can vary in length. Many stream files contain what is essentially human readable form: strings of data, sometimes delimited with commas or tabs, with a carriage-return and/or linefeed at the end of each record. Other stream files may include images or other binary data, such as programs or compressed files.

 

LOBs are the way that traditional relational databases deal with the variable-length data. Relational databases have VARCHAR fields, which support smaller amounts of data, but for anything larger than about 32K (depending on the database), relational databases turn to LOBs. DB2 supports three kinds of LOBs: BLOBs, CLOBs, and DBCLOBs. Each is designed for different content. BLOBs are Binary Large Objects and are primarily intended for things like images and other binary data. CLOBs are used to store traditional character data like email messages or text documents. DBCLOBs are like CLOBs except that they support double-byte data. We'll see in a moment where these data types come into play.

The IFS and the Incredible Unshrinkable User Profile

This first article will focus on the downside of a high-volume IFS implementation. The key attribute here is high-volume. As long as your use is reasonable, the IFS can serve your purposes just fine. It acts like any other directory system you may be used to, whether it's Windows-based or a UNIX variant. In fact, the IFS can be used just like any other folder system, and mapped drives allow you to copy files and folders and basically just run your system. If you're used to copying files to a folder and processing them in batches, the IFS provides the location, and the IBM i has all the APIs to allow access from high-level languages like RPG. You can loop through a folder and process the files one at a time, opening them and reading them into your program. You can also write stream files to be used by other systems, whether it's a simple comma-delimited file or a full-blown Excel spreadsheet.

 

This may not be news to you; many shops have been using these capabilities for quite some time now. But the whole idea became much more interesting to me with the explosion of XML processing in the industry. XML is a perfect example of a stream file: the data not only doesn't have fixed-length records, but the data is hierarchical in nature, with different data in each line. The data in a given XML tag is context-sensitive, based on where in the document it is located, so you can't really look at a single tag in isolation even if you could jump to it with a single read. So the only way to really store XML data (for now) is as a stream file.

 

And as I said already, this is a perfectly adequate method, until you get to higher volumes. At that point, the IFS becomes a less-friendly environment.

 

How unfriendly? Well, there are two stages. The first is predictable, readily diagnosed, and mostly just annoying. In many load-related problems, you only see issues only when the system reaches some unspecified threshold and the wheels start to come off the machine. In this case, there's a very specific point where things break down: 16383. To paraphrase Jeff Foxworthy, if you recognize that number you may be a geek. It's 2^14 – 1, but what it represents is the maximum numbers of files in a folder before it begins to lose functionality. After this point, many system functions begin to fail. This occurs most noticeably in the Qshell and PASE environments; any system function you might attempt to run over that folder will terminate with an error message related to too many files. This happens when you try to move them, delete them, ZIP them up using the jar command, you name it. Basically anything you try to do inside the shell environments fails. You can still execute the native IBM i commands such as MOV and DEL, but that doesn't help if you're trying to archive them.

 

And why would you do that?

 

Well, that brings us to the more significant of the two problems: the ever-expanding user profile and the never-ending SAVSECDTA. You see, every object you own or have specific authority to gets an entry in your user profile. Files, programs, data areas, you name it, there's an entry in the user profile. Which means that if you own or are authorized to thousands of objects, you have thousands of entries in your user profile. Note the magnitude, though: thousands of objects, or maybe tens of thousands, is the high end for a typical IBM i shop.

 

However, it's nothing to add hundreds of thousands or even millions of stream files in a high-volume transaction shop. In that case, the user profile that adds those files grows and grows. The more files, the bigger the user profile. If you have millions of files, the user profile can grow to a gigabyte or more in size, and SAVSECDTA starts to get measured in hours. Not only that, but thanks to the way the folders work, anybody who has authorization to the folder where these files are created also gets authority to the files, so those profiles grow as well.

 

And the real problem is that no way exists to shrink those user profiles. Even after you've removed all the entries, the index space remains and there's no way to reclaim it short of deleting the user profile. In fact, unless you plan to get rid of that user profile completely, you'll need to create a second temporary user profile, delete the first profile and transfer ownership to the temporary folder, recreate the offending user profile, and then delete the temporary user and transfer ownership back to the original. Not the sort of thing you want to do on a regular basis.

 

To alleviate this problem, start out by assigning an authorization list to your high-volume IFS folders. This will at least help to minimize the authority-related entries for your IFS files. However, the only long-term solution is to get away from the IFS for your stream files entirely, and that's where LOBs come in. I'll show you more about those in a later article.

Joe Pluta

Joe Pluta is the founder and chief architect of Pluta Brothers Design, Inc. He has been extending the IBM midrange since the days of the IBM System/3. Joe uses WebSphere extensively, especially as the base for PSC/400, the only product that can move your legacy systems to the Web using simple green-screen commands. He has written several books, including Developing Web 2.0 Applications with EGL for IBM i, E-Deployment: The Fastest Path to the Web, Eclipse: Step by Step, and WDSC: Step by Step. Joe performs onsite mentoring and speaks at user groups around the country. You can reach him at This email address is being protected from spambots. You need JavaScript enabled to view it..


MC Press books written by Joe Pluta available now on the MC Press Bookstore.

Developing Web 2.0 Applications with EGL for IBM i Developing Web 2.0 Applications with EGL for IBM i
Joe Pluta introduces you to EGL Rich UI and IBM’s Rational Developer for the IBM i platform.
List Price $39.95

Now On Sale

WDSC: Step by Step WDSC: Step by Step
Discover incredibly powerful WDSC with this easy-to-understand yet thorough introduction.
List Price $74.95

Now On Sale

Eclipse: Step by Step Eclipse: Step by Step
Quickly get up to speed and productivity using Eclipse.
List Price $59.00

Now On Sale

BLOG COMMENTS POWERED BY DISQUS

LATEST COMMENTS

Support MC Press Online

$

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: