• Guru: Using Mixed Lists To Add “Data Structures” To CL Commands

  January 15, 2024 Ted Holt

  I can’t remember the last time I worked on an RPG program that had no data structures, but it was probably on a System/34. Everybody uses data structures, and with good reason – they are as handy as a pocket. When writing CL commands, it is possible to include parameters that are formatted as data structures. IBM calls them mixed lists. In the following paragraphs, I show how this is accomplished.

  You may not realize it, but you have used IBM-supplied commands that have mixed-list parameters. For example, the Copy File (CPYF) command has several such parameters: FROMKEY, TOKEY, INCCHAR, …

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• Guru: Partitioning Result Sets Using SQL

  November 27, 2023 Mike Larsen

  While working on a project recently, I needed to retrieve attributes of an item. While that sounds like a simple task, there was a twist. While reviewing the contents of the item master table, I noticed there could be multiple rows for the same item and each row was active and valid from a business perspective.

  I won’t get into the business end of it, but my goal was to return the most recent iteration of the item for further processing in the program. After doing some research and trying some potential solutions, I came across the SQL partition by …

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• Guru: Procedure Driven RPG Means Keeping Your Variables Local

  November 6, 2023 Gregory Simmons

  One of the things I love most about procedure driven RPG is that it allows me to keep my variables locally defined. Imagine this horror story that happens all too often in RPG shops.

  Jake: “Hey Gregory, Accounting just called; seems the rebalancing report program is acting up. Didn’t I hear you were working on that the other day?”

  Me: “Ugh, yes. All I had to do was reset this field that was used to show or not show the totaling line between branches. I tested in my library and the fix worked fine.”

  Jake: “Yeah, I had to change …

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• Guru: The Transition From Modern RPG IV To Modern SQL

  October 30, 2023 Bob Cozzi

  Seven or eight years ago I was working with a client who needed more contemporary reporting than provided by the legacy Query/400 product. Initially I looked at Db2 Web Query and realized the documentation was sparse and the tutorials for most things, even “getting started” were virtually non-existent. It was also about four times more expensive than I felt it was worth to a P05 or P10 client. I mentioned the documentation issue to the folks at IBM and they agreed. Some of it was eventually resolved, but not enough in my opinion to get the masses to replace Query/400 …

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• Guru: Search Source Code For Strings Using SQL

  October 9, 2023 Bob Cozzi

  The IBM-supplied Find String Using PDM (FNDSTRPDM) command and PDM option 25 are how most developers scan for a simple value in a list of source file members. But what if you need more? For example, what if you want to find something complex, such as the field named “CUST” but not the field named “CUSTNAME” “CUSTOMER” or “CUSTNO”? Go ahead, I’ll wait?

  While I do use FNDSTRPDM all the time, I now use the SQL READSRC (Read Source File Member) Table function more often.

  READSRC SQL UDTF

  The READSRC SQL Table function or UDTF (User-defined table function) uses an …

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• Guru: TryIT – You’ll Like It

  October 2, 2023 Ted Holt

  I have watched children play Whac-a-mole, but I’ve never played it myself, perhaps because the game unpleasantly reminds me of programs that I have had to work on. I fix one bug, only to see another bug rear its ugly little head. Life’s too short to endure such nonsense. Besides, it is embarrassing for someone to tell me that the program I supposedly just fixed is still broken.

  Suppose you’re working on a 4,000-line RPG program and you comment out lines 650-660. What you don’t realize at the time is that a variable used in line 2755 has to …

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• Guru: Procedure Driven RPG With Linear-Main Programs

  September 11, 2023 Gregory Simmons

  A number of years ago, I started migrating away from writing subroutines and started writing procedures instead. Yes, quite often, this was simply because it was “new and shiny” and served no real benefit from their subroutine counterpart. However, as the language and I evolved, I found that my method of approaching every project was what I call procedure driven RPG.

  Let’s have a look at a simple RPG program. In this little program, to give it a purpose, I’m going to have a little fun with math and demonstrate the Fibonacci sequence:

  1	**Free
  
  2	Dcl-s i    Uns(3) Inz(3);
  

  …

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• Guru: Retrieving The Long And Short Object Name

  August 14, 2023 Bob Cozzi

  Many releases ago, IBM i received “Long SQL Names” for files and libraries. These new longer names (up to 128 characters) were well received by SQL enthusiasts, but largely ignored by the mainstream IBM i developer. As each version of IBM i emerged, more and more shops experienced one or more objects with a longer-than-10-character name.

  Recently I created a file named BOAT_TRAFFIC. This name is clearly longer than 10 characters. I used SQL DDL (the CREATE or REPLACE TABLE statement) to create the file. Using SQL DDL is the only real way to create an object with a long …

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• Guru: Object Usage Statistics

  July 10, 2023 Bob Cozzi

  A long time ago in a system far, far away, IBM added the Date Last Used to the Object Description for all objects on the system. The term “last used” means different things to different object types; for *FILE objects it means the file was opened or its description was changed, for *PGM objects it means the program was called, for other objects it generally means what you might think it means (viewed, retrieved/read, updated, etc.) The only exceptions are Device Descriptions which get updated when a *DEVD changes from “Vary On Pending” to some other status.

  The Date Last …

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• Guru: Binding Directory Entries

  June 5, 2023 Bob Cozzi

  I assume you’ve heard about *BNDDIR (Binding Directory) objects introduced circa 1994 with OS/400 V3R2. The infamous QC2LE binding directory is used by a huge number of RPG applications to access C runtime and unblocked MI functions such as system cvthc, cpybytes, and matmatr. You have probably seen RPG IV source code with the BNDDIR(‘QC2LE’) keyword on the header specification.

  I was one of the first developers outside of IBM to use Binding Directories for my own code. When I go back and look at my own RPG IV code created prior to mid-2007, well over 90 percent of it …

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