Discovering how much personal storage space remains

This post is based upon something I made for myself, and after discussing it with some friends they said it would be worthy of becoming a post as others have the same need.

All of the code shown on this blog is written on servers generously provided by the IBM i hosting provider RZKH. Their hosting package gives me a fixed amount of storage, disk space, which I can use. While I am a careful user, who deletes all objects when I have finished with them and regularly clears my output queue, I want an easy way to see the following:

1. How much storage space was I allocated when my profile was created?
2. How much space have I used?
3. How much space do I have left I can use?
4. What percentage of my allocated space have I used? If I reach a certain percentage I know I need to start deleting and clearing immediately

Modern RPG Redbook updated version now available

A new draft of the IBM Redbook "Who Knew You Could Do That with RPG IV? Modern RPG for the Modern Programmer", completed October 20 2016, has been made available. I recognize many of the authors as people I respect as highly knowledgeable in the use of modern RPG.

The chapters cover many items which should interest anyone using, or wanting to learn, modern RPG:

Validation trigger in RPG

When I wrote about creating a validation trigger in SQL several people asked me to give an example using RPG. Never being one to turn down a challenge this post is going to show how to do the same as my SQL example, but completely in RPG.

I am not going to go into the reasons why you might want to consider using validation triggers, as I gave my opinion in the previous post.

I started my previous example giving an example of a SQL DDL table, in this example I am going to use a DDS physical file. FILE1 has three fields:

Who remembers these? Print charts

I could not resist posting pictures of a find I made in a box at home, a pad of IBM 132/10/8 print charts. The numbers denote that the chart is 132 characters wide, with 10 characters per inch and 8 lines per inch. These were used to assist programmers designing reports, and make it easier to translate the desired layout to Output specifications.

My wife had acquired the pad of charts in a previous job many years ago, and had put it in a "safe place" in case she needed them in the future. The charts had been stuffed into box of other old computer items during one of our moves, only to be rediscovered yesterday during one of those "I wonder what's in that box?" moments.

Creating a program to show jobs in message wait

I do get many requests asking for whole example programs, especially ones with a subfile, rather than just bits and pieces of code that I usually give in these examples. With this in mind this post brings a number of things I have written about before together into one program, which I thought would be an interesting refresher. So here goes...

I was asked to write a program to only show jobs that are in message wait status, and I want to add the ability give the user some options that would allow the user to analyze the error and reply to it.

To summarize what I need to do:

Coping with null with derived columns

I was assisting a colleague creating a SQL View when I encountered something I had not thought of before. He wanted to create a view with a derived column based on a column in the "right" table of a LEFT OUTER JOIN. Everything looked fine until the LEFT OUTER JOIN did not find a row in the "right" table. We could easily stop a null appearing for the columns from the "right" table, but what about the derived column?

Null is a concept that many people struggle with. I often have had to explain what null is and why it is different from blank or zero to older RPG programmers, who always have a confused or dismissive look in their faces. Users just don't understand the concept. This is why when I create output I always put some value in the column that comes up null.

Validation trigger

Triggers are a versatile database tool. A few weeks ago I wrote about using triggers to write data to an output file. I can also use triggers to validate data before it is written to the file or table. By placing the business rules and validation processes into the database with a trigger guarantees that:

1. The same business rules are used every time. If the rules change I just need to change the logic in the trigger, rather than find all of the programs that output to the file and change the logic within them.
2. It is not possible to circumvent the trigger. No matter which programming language or tool I use with the file the trigger will be executed. I will no longer have to worry about a rogue colleague changing data behind the scenes using something like DFU.