Programming

Book Review: Subfiles in Free-Format RPG

Fri, 20 Dec 2013 06:00:10 +0100

Whether you're a newbie or a seasoned pro, this book has something for you. Written by Mike Faust For System i developers, mastering the ability to develop subfile applications is an absolute must! In Subfiles in Free-Format RPG, Kevin Vandever takes the reader through the subfile concept—from start to finish. Unlike other books on the topic, this one specifically focuses on coding subfile applications in free-format RPG and does an excellent job of explaining how to use subfiles in the moder...

What Everyone Should Know: Where to Start

Wed, 18 Dec 2013 06:00:15 +0100

There's so much to learn today, and the "to learn" pile just keeps getting bigger and bigger while our time to learn it seems to shrink. So what's a body to do? Written by David Shirey Do you ever feel depressed? Professionally that is? Like there is so much to learn and there is no way you're going to be able to squeeze it into your already overloaded day? Yeah, me too, and I am easily depressed to begin with, so it wreaks havoc with my id. But I can't escape it. The days of...

The API Corner: Determining Whether Jobs Are Currently Active

Wed, 18 Dec 2013 06:00:10 +0100

Build your own API using the List Jobs System API. Written by Bruce Vining I was recently asked by Mark H. if there's an easy way to determine whether a given job, using only a simple job name such as DAYEND rather than a qualified job name such as 123456/ABC/DAYEND, was currently active on the system. From my point of view, it's easy enough to call some system APIs to determine this, but he would prefer for application developers to just make a simple call to a function that, at a mini...

Using ASNA Mobile RPG to Create a Mobile App

Wed, 18 Dec 2013 06:00:05 +0100

ASNA Mobile RPG puts mobile programming capabilities easily in the hands of RPG programmers using nothing but RPG! Written by Roger Pence ASNA Mobile RPG is a product that empowers RPG programmers to create great mobile apps for smartphones and tablets using only RPG. There's no need for JavaScript, HTML, Objective C, Java, PHP, or any of the other languages typically used for mobile development. One of the hallmarks of great mobile applications is that they are able to ...

Book Review: Functions in Free-Format RPG IV

Fri, 13 Dec 2013 06:00:15 +0100

This one short volume manages to essentially be both a general introduction and a detailed reference. Written by Joe Pluta With Functions in Free-Format RPG IV, Jim Martin has done it again. Jim has a particular expertise in taking a highly technical topic and distilling it into just a couple of hundred pages, making it accessible to any IBM i programmer. Jim also has a knack for identifying just the right balance of general knowledge and technical detail, and this book demonstrates that sense ...

Practical RPG: Data in the Cloud, Part 1

Wed, 04 Dec 2013 06:00:15 +0100

The cloud has become ever more ubiquitous, but with so many choices it's hard to know what fits your business; this article will help you begin to sort through things. Written by Joe Pluta Cloud-based data is a huge topic. Nowadays, you can find everything in the cloud, from simple file storage to entire applications. Software-as-a-service (SAAS) has mushroomed and morphed into a plethora of virtual services. The problem with such a variety is trying to identify which services and provi...

Investigate the Undocumented _LSPCO System Built-in

Wed, 04 Dec 2013 06:00:10 +0100

The _LSPCO system built-in accepts a space pointer as its input and returns the origin of addressable storage of the "space" addressed by the space pointer. Written by Junlei Li In my previous article, A More Complete View of the Machine Interface of IBM i, I introduced a technique that Gene Gaunt invented to retrieve all system built-ins supported by an IBM i release. You might have noticed that many of the system built-ins retrieved via Gene's technique have never been documented publ...

PHP: Variables, Arrays, and Functions: The Final Chapter

Wed, 20 Nov 2013 06:00:15 +0100

This is the last step in understanding how variables, arrays, and functions are similar, are different, and come together to form the basis of the PHP universe. Written by David Shirey So far in this series, we have covered variables and arrays. Granted, it took us three months to cover arrays and how to display them, but let's not worry about that now. In the process, we saw that variables were preceded by a dollar sign ($) and consisted of underscores plus any alphanumeric digits (that i...

The API Corner: Verifying That Nothing Has Changed, Part 2

Wed, 20 Nov 2013 06:00:10 +0100

Explore more options with the Calculate Hash API. Written by Bruce Vining Last month, in Verifying That Nothing Has Changed, we saw how easy it can be to create a hash over a string such as 'Some data to be hashed' by using the Calculate Hash API. We also saw how the calculated hash value is very dependent on what data is being hashed. Something as simple as a trailing blank or a punctuation change can cause significant changes in the derived hash value. Today, we'll look at some options on how...

Application Lifecycle Management: Some Definitions (and Misconceptions)

Mon, 11 Nov 2013 06:00:15 +0100

Integrated Application Lifecycle Management (ALM) provides the ability to innovate while reducing overhead costs, thus improving time to delivery, quality, value, and predictability. Written by Olenka Van Schendel The classic definition of Application Lifecycle Management (ALM) derives from the notion of "software as a product": identifying distinct and cyclical phases of requirements management, software architecture, development, testing, maintenance, change management, project management, a...

Practical RPG: Technology Refresh 7 First Look

Wed, 06 Nov 2013 06:00:15 +0100

Technology Refresh 7 (TR7) provides quite a few new features, and this is the first article devoted to some of those changes. Written by Joe Pluta TR7 has a wealth of additional features and functionality for various parts of the IBM i operating system, and in coming articles I plan to cover as many of them as possible. But since the focus of today's article is RPG, it makes sense to stick with the enhancements in RPG-related compilers. So let's take a look at what has happened....

Manage Automatic Storage Dynamically via Modify Automatic Storage Allocation (MODASA)

Wed, 06 Nov 2013 06:00:10 +0100

Learn the fantastic automatic storage frame (ASF)-operating MI instruction and the implementation details behind it. Written by Junlei Li From the point of view of a programmer, the ability to change the automatic storage allocation at run time would be fabulous. Automatic storage is thread-private storage; therefore, in a multi-threaded environment you don't need to worry about thread synchronization when you store your program variables in automatic storage. Automatic storage is managed by th...

PHP: Variables, Arrays, and Functions, Part 3

Wed, 16 Oct 2013 06:00:15 +0100

Use the foreach PHP command to get data out of a mult-dimensional array. Written by David Shirey We're going to do one last piece related to arrays in PHP. Why? Because when you're using PHP to put data out onto a page or read data in from a page, you'll use arrays as the intermediary between your file and your page. Consequently, knowing how to deal with them is very important....

The API Corner: Verifying That Nothing Has Changed

Wed, 16 Oct 2013 06:00:10 +0100

Learn what the Calculate Hash API can do for you. Written by Bruce Vining In the past month, I've been asked two related questions. The first was "Can my AS/400 [sic] work with hashes?" and the second, a bit more specific, "Can the i generate a SHA-256 hash to work with a Linux system?" The answer to both questions, as you might expect, is yes, there's an API for that (as long as the system is at V5R3 or higher that is, in the case of the AS/400 question)....

Practical RPG: BIFs and Expressions

Wed, 02 Oct 2013 06:00:15 +0100

Built-in functions (BIFs) allow you to significantly reduce the maintenance code in programs; here's an example. Written by Joe Pluta Built-in functions (BIFs) are designed to make programmers more productive. They do this in a number of ways, but one my favorites is how they reduce the number of lines of code in my programs. If you've used BIFs you're probably already familiar with how they simplify your code; for example, date manipulation is far simpler using the %date BIFs. Today, though, I...

A More Complete View of the Machine Interface of IBM i

Wed, 02 Oct 2013 06:00:10 +0100

Learn a creative technique that Gene Gaunt invented to retrieve all system built-ins supported by your IBM i. Written by Junlei Li Since System/38, as a high-level machine interface, the Original Machine Interface (OMI) instruction set described a complete, elegant object-based architecture of the system. The OMI instruction stream, along with other components (e.g., the object definition table (ODT)) stored in the program template of an MI program object, allows the MI program to be translated...

PHP: Variables, Arrays, and Functions, Part 2

Wed, 18 Sep 2013 06:00:15 +0100

Love the idea of putting data in two-dimensional arrays? Well, the next step is figuring out how to get it out. But before you do that, there's one little thing. Written by David Shirey In our last visit, we talked about arrays. We talked about the difference between numeric and associative arrays. We talked about how to load and unload data from them. And we talked about how to load data into two-dimensional associative arrays, which more or less mimic file records. Let's face it, we just co...

The API Corner: Manipulating a Job's Library List

Wed, 18 Sep 2013 06:00:10 +0100

Learn what the Change Library List API can do for you. Written by Bruce Vining I recently received a note from Shawn W. related to a situation in which he needs to significantly change a job's library list, perform a function, and then restore the job's library list to the original values. In his case, a corporation on one System i might have multiple instances of an entity (multiple plants, multiple companies, etc.) with each entity having multiple libraries associated with it (inventory libra...

Practical SQL: Variables in SQL

Wed, 04 Sep 2013 06:00:15 +0100

One problem with complex queries is keeping all the pieces in sync; this technique helps you do just that. Written by Joe Pluta I've long extolled the virtues of common table expressions (or CTEs), and I've also showed you how to use UNION statements to great advantage. They're powerful, and I find them particularly well suited to performing ad hoc analysis on production data. Unfortunately, both of those techniques can fall prey to a very specific problem that has caused me severe headaches in...

Genuine Dynamic Program-Exported External Data in IBM i

Wed, 04 Sep 2013 06:00:10 +0100

Learn the native dynamic external data mechanism we have had since System/38. Written by Junlei Li As an IBM i developer, you might be proud of the numerous dynamic features in either the OS level or the machine interface (MI) level that allow our developers to produce more reliable and maintainable software products with less effort. For example, the Override commands allow programmers to override (replace) a file that is used by a program or override certain parameters of the file being proce...

What You Should Know About the Format of Records Saved to a Save File, Part 2

Wed, 21 Aug 2013 06:00:15 +0100

Do you need to retrieve data from variable-length fields of deleted records? Written by Juan Macias The data of variable-length fields of records deleted from a file can be retrieved provided that the inserts and updates performed in the file after the records were deleted didn't affect the variable part of the file....

The API Corner: Accessing Job Queue Entries

Wed, 21 Aug 2013 06:00:10 +0100

Use the Open List of Jobs API. Written by Bruce Vining In last month's column, "Monitoring a Job Queue from an RPG Application Program," we looked at how an application program could be notified, via data queue messages to a user-specified data queue such as BVINING/MYDTAQ, when a job is submitted to a job queue such as BVINING/MYJOBQ....

The Perils of Activation Groups Gone Awry

Wed, 07 Aug 2013 06:00:15 +0100

Controversy surrounds the use of service programs in the default activation group, and this article explains a very specific and painful reason to avoid it. Written by Joe Pluta You've probably heard that programs written for the Integrated Language Environment (ILE) don't work and play well with legacy programs written using the Old Program Model (OPM). And if you're like me, you've probably tried them together to see what would happen. This isn't something we do cavalierly; instead, it's usua...

1001 Activation Groups Within a Single Job

Wed, 07 Aug 2013 06:00:10 +0100

The solution revealed in this article allows you to start user-defined activation groups and run programs in them. Written by Junlei Li Have you seen an IBM i job containing more than 1000 activation groups? If not, you can call the following seven-line CL program (agp1001.clp) in an interactive job and then issue a DSPJOB OPTION(*ACTGRP) command to check what you get....

PHP: Variables, Arrays, and Functions (Don't Say It)

Wed, 17 Jul 2013 06:00:15 +0100

You've used arrays in RPG, but they're so much more important in PHP. Written by David Shirey Last May, we talked about variables and how they're used in PHP. If you were paying any attention, which I wasn't, you know that PHP supports the following variable types: string (alphanumeric), integer, floating point (decimals), Boolean (true or false), array, object, null, and resource. Now we want to zero in on one of those variable types that we talked about—namely, arrays—and look at how they...

The API Corner: Monitoring a Job Queue from an RPG Application Program

Wed, 17 Jul 2013 06:00:10 +0100

Today, we'll look at using the Job Notification Exit Point. Written by Bruce Vining In last month's column, "Monitoring a Job Queue," we looked at a CL program that, via data queue messages sent by the system, enabled us to become aware of newly submitted jobs to a job queue and automate the release of those jobs. This month, we'll provide that level of automation, and a bit more, using an RPG program....

Practical SQL: OLAP, Part 2

Wed, 03 Jul 2013 06:00:15 +0100

In this next installment on SQL's Online Analytical Processing (OLAP) functions, you'll see how OLAP continues to provide SQL users the business functions we've enjoyed in RPG for so long. Written by Joe Pluta In my previous OLAP article, I used the OLAP function ROW_NUMBER to provide the concept of "next record" that we take for granted in RPG's native access (contrast RPG's native ISAM access with SQL's relational access). In this article, I'll show you the magic of GROUPING SETS and how they...

Change the Last-Used Date of an IBM i System Object Arbitrarily

Wed, 03 Jul 2013 06:00:10 +0100

A practical tool program can achieve that goal. Written by Junlei Li When issuing a DSPOBJD DETAIL(*FULL) command on an IBM i object, you might have noticed the Last used date field in the Change/Usage Information portion of the result display. As its name indicates, the Last used date attribute is the date on which the object was used the last time. As you probably know, the last-used date attribute is not stored in the Object Information Repository (OIR) space of the context in which the obje...

The Once and Future PHP

Mon, 24 Jun 2013 06:00:15 +0100

Where has PHP been, where is it now, and where is it going? Written by Thomas M. Stockwell PHP, the incredibly popular server-side scripting language originally created by Rasmus Lerdorf in 1995, has become one of the greatest success stories of the open-source software movement. Today, PHP is estimated to be installed on millions of web servers worldwide, fueling an estimated 244 million websites. Some analysts claim that over 90% of the Internet is enabled by PHP scripts. Yet, ironically,...

Storing Metadata the Profound UI Way

Mon, 24 Jun 2013 06:00:10 +0100

Discover the benefits of using RPG OA and JSON to store metadata in the display file. Written by Scott Klement Editor's note: This article introduces the white paper "Storing Metadata the Profound UI Way" available free from the MC White Paper Center. While RPG Open Access is nothing new, there's still some confusion in the IBM i community as to what it is and how it's used. Additionally, there has also been much talk lately about Open Access metadata and how it should be leveraged wi...

Cool Things: ILE RPG as a Web Services Client

Fri, 21 Jun 2013 06:00:15 +0100

Use IBM's Web Services Client for ILE to consume a web service in an ILE RPG program. Written by Mike Faust Web services serve many purposes—from utilizing external web services for things like retrieving exchange rates or tracking shipments, to using internal web services as a means of communicating between applications within your organization. The task of writing a program to consume a web service can be relatively simple or very complicated, depending on the requirements of the web servic...

The API Corner: Monitoring a Job Queue

Wed, 19 Jun 2013 06:00:15 +0100

Learn the value of using the Job Notification Exit Point. Written by Bruce Vining Back in April, the following question was posed on the MC Press Online CL forum: "I am looking for advice on how to create a CL that will actively monitor a specific job queue and release jobs. All jobs that are submitted automatically go to hold status because the JOBD for end users is set to this. The business does not want to change the JOBD, so I need to come up with a way to actively monitor jobs for...

RPG IV Style: Free-Format Syntax

Wed, 19 Jun 2013 06:00:10 +0100

If you use the free-format specification, good standards will result automatically. Written by Bryan Meyers and Jim Buck Editor's Note: This article is an excerpt from the book Programming in RPG IV, 4th Edition. At current releases, RPG IV is primarily a free-format language, especially in the area of calculation processing. While it's not perfect, the free-format specification effectively renders the traditional fixed-format Calculation specification obsolete. IBM has introduced many ne...

Introduction to SQL, Part 5

Wed, 12 Jun 2013 06:00:15 +0100

Editor's note: This article is an excerpt from Mastering IBM i, published by MC Press. Written by James Buck and Jerry Fottral An additional feature of the Run SQL Scripts interface is SQL Assist. This feature allows the user to create fairly sophisticated SQL statements with little or no knowledge of SQL. Although you should learn to write SQL statements without depending on a feature such as SQL Assist, this is a great tool to help you, as a new SQL programmer, to develop SQL statements while...

Practical RPG: BLOBs, CLOBs, and XML Part 2

Wed, 05 Jun 2013 06:00:15 +0100

You want to use LOBs in your RPG program but don't know where to start; read this article to find out how! Written by Joe Pluta In the first article in this series, I identified situations where it is preferable to store stream data in a database rather than in the IFS. Specifically in my case, I had literally millions of stream files proliferating in the IFS and causing some real processing issues. My alternative was to store the stream files in the database. Implementing LOBs is not difficult...

Access Database Files Dynamically in RPG

Wed, 05 Jun 2013 06:00:10 +0100

Learn how to access database files via the UFCB. This practical example repairs invalid data in OPEN fields due to DBCS character truncation in a random database file. Written by Junlei Li Programs written in IBM i high-level languages (HLLs) such as RPG are bound to files they access statically, or in other words, at compile time. However, in VRM610, RPG was enhanced to allow passing files as parameters to RPG programs and procedures (see File Parameters). The enhancement makes accessing files...

PHP for RPG Programmers: Variables, Arrays, and Functions

Wed, 15 May 2013 06:00:15 +0100

PHP makes use of variables, arrays, and functions. But can you tell them apart? Written by David Shirey In my last column, we talked about some of the special operator symbols that PHP uses, which can be really confusing when you read PHP unless you're familiar with them. Remember what they were? Remember the -< operator? Really, you do? That's so sad then because there is no such operator (at least as far as I know, although I would hate to put any serious money on it; PHP operators seem t...

The API Corner: Just What Release Am I On?

Wed, 15 May 2013 06:00:10 +0100

Find out by using the Retrieve Product Information (QSZRTVPR) API. Written by Bruce Vining A question that seems to come up on a regular basis is "How can a program tell what release level of the operating system it's running on?" To answer this question, we'll look at a category of system APIs that many of you may not have reviewed in the past—the Software Product APIs, which are introduced here....

Practical RPG: BLOBs, CLOBs, and XML Part 1

Wed, 01 May 2013 06:00:15 +0100

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

Simon's Solutions: Exploring the QSCMATPG and QSCCRTPG APIs

Wed, 01 May 2013 06:00:10 +0100

Open the door to the OMI program template. Written by Junlei Li In a post in the MI400-L mailing list at midrange.com, Simon Coulter documented the Materialize Program (QSCMATPG) and Create Program (QSCCRTPG) APIs in detail, including the parameter lists and related usage notes. Simon also designed a couple of CL commands to make it easier and more secure to use these APIs. With this information, you can open the door to the Original MI (OMI) program template, which allows a System/38 program t...

What You Should Know About the Format of Records Saved to a Save File

Wed, 17 Apr 2013 06:00:10 +0100

When a file contains variable-length fields, the data of the fixed-length fields of its deleted records can still be retrieved. Written by Juan Macias A known technique to retrieve the records deleted from a file consists of saving the file to a save file and extracting the records from the save file. This technique is based on the fact that, in many cases, the records of the file are stored in the save file maintaining their format, apart from a status byte added by the system at the beginning...

Introduction to SQL, Part 4

Wed, 10 Apr 2013 06:00:15 +0100

Editor's note: This article is an excerpt from Mastering IBM i, published by MC Press. Written by James Buck and Jerry Fottral SQL's version of a logical file is a view. Although a view is conceptually similar to a logical file, SQL's greater flexibility and ability to use functions and expressions make views far more powerful than logical files. For example, in a logical file there is no way to select group summary records based on the value returned by a column function, as we did in the fina...

Practical SQL: OLAP, Part 1

Wed, 03 Apr 2013 06:00:15 +0100

Online Analytical Processing (OLAP) adds a variety of processing features to SQL syntax that makes it much more useful as an ad hoc analysis tool, and this article introduces the first of those functions. Written by Joe Pluta SQL has always been a great tool for querying data. The problem is that SQL doesn't always lend itself to the sort of pattern analysis that's needed in enterprise data processing. Something goes awry in the database and the only way to identify the source of the problem is...

Be Kind to Your DBCS Data

Wed, 03 Apr 2013 06:00:10 +0100

Learn how to ensure the validity of extended character string assignment via the CPYECLAP instruction. Written by Junlei Li IMHO, high-level languages (HLLs) in IBM i do not treat character strings containing double-byte character set (DBCS) characters seriously enough. For example, assigning a long character string containing DBCS characters to a shorter character variable using the EVAL operation code of RPG would probably truncate the DBCS data in the source string and therefore lead to an i...

Weird, Simple Stuff in PHP: Operators

Wed, 20 Mar 2013 06:00:15 +0100

Yeah, they're sort of the same as in RPG…but not really. Written by David Shirey Over the last few articles, I have been on a PHP kick, talking about the language in general and how it integrates into the i in particular. The next step, in the twisted overgrown forest that is my mind, is to take a look at some specific things in PHP that are different from what we're used to in RPG. Not a tutorial, but maybe an appendix to the tutorial or book you might be using if you're trying to make that ...

The API Corner: Determining Key Values

Wed, 20 Mar 2013 06:00:10 +0100

Let's return to the Retrieve Database File Description (QDBRTVFD) and Copy Numeric Value (CPYNV) APIs. Written by Bruce Vining In developing a general-purpose utility to detect decimal data errors, we have made use of a few APIs. In the article "In Search of Decimal Data Errors," we saw how the List Fields (QUSLFLD) API can be used to find all numeric fields, within a user-specified file record format, that are defined as either zoned decimal or packed decimal. In addition to discovering the da...

Introduction to SQL, Part 3

Wed, 13 Mar 2013 06:00:15 +0100

Editor's note: This article is an excerpt from Mastering IBM i, published by MC Press. Written by Jim Buck and Jerry Fottral If you tell SQL to retrieve rows that have the same column values, it will do that, duplicating those rows in the result table. For example, if you wanted to list the employee numbers of any employees assigned to any project, you might simply type......

Practical RPG: Flexible Parameters, Part 3

Wed, 06 Mar 2013 06:00:15 +0100

As we move to service programs, OPM RPG programs get left out in the cold, but creative parameter use can keep them in the mix until you get a chance to convert them. Written by Joe Pluta Encapsulating business logic is all about parameters. In the first article in this series, I covered optional parameters. In the second article, I introduced service programs into the mix by using a service program as an adapter to an existing RPG program with a complex parameter list. Service programs are the...

Convert Authority Special Values to and Back from MI Authority Bits

Wed, 06 Mar 2013 06:00:10 +0100

Learn a basic authority-related technique along with a practical Print Private Authorities utility. Written by Junlei Li In IBM i, there are authority special values defined at the OS level, which are used by authority-related CL commands and APIs, and there are other authority special values defined at the Machine Interface (MI) level, which are used by Authorization Management MI instructions. The meanings of these two sets of authority values are almost identical; however, their representati...

The CL Corner: More Character-String Enhancements for CL

Fri, 01 Mar 2013 06:00:15 +0100

Let's look at the new %CHECK, %CHECKR, and %SCAN built-ins of CL. Written by Bruce Vining In last month's article, "How Would You Like That Character String Trimmed?," we reviewed the new CL built-ins %TRIM, %TRIML, and %TRIMR. This month, we'll look at three more CL built-ins that IBM has provided by way of 7.1 PTF SI49061. The new built-ins, which are supported with both the OPM and ILE compilers, are %CHECK, %CHECKR, and %SCAN....