RPG400 manuals found

In my previous post I stated that IBM had removed the RPG400 user's guide and reference from the KnowledgeCenter.

Having performed a good deal of searching of the internet I have been able to find copies of both of these manuals in a dark corner of the IBM website. The manuals are from 2000. That may seem a long time ago for a "current" manual, but RPG3 has not been enhanced since RPG4 was introduced 23 years ago.

I have uploaded both of these PDF files to my Dropbox account, and you can reach them by using the following links:

• RPG user's guide:  view   download
• RPG400 reference:  view   download

Having given you these links I trust you will only refer to these manuals to remind yourself of some of the anachronisms of old RPG, rather than use to develop new code.

RPG400 manuals no longer available

As I have said in previous posts if you are programming only in RPG400, or RPG3, and not learning and using the latest version of RPG you are risking your future.

I found further proof yesterday browsing IBM's KnowledgeCenter looking for the latest RPG reference manual, when I noticed that the RPG400 (RPG3) manuals are no longer offered on line.

The following manuals are not included in the IBM i Information Center...

• RPG/400 Reference...
• RPG/400 User's Guide...

Searching strings using SQL

In a previous post I had written about using regular expressions to search for data within a string, but I did not mention the easier to use LOCATE_IN_STRING SQL scalar function. I believe this was introduced as part of IBM i Technical Refresh 2 for 7.3 and TR6 for 7.2.

The LOCATE_IN_STRING has four parameters:

1. The source string to be searched (mandatory)
2. The string used to search (mandatory)
3. Starting position (optional)
4. Instance, which number occurrence to find (optional)

I created a SQL DDL table, which I called TESTFILE, which I will be using in these examples. It contains one column, called DESCRIPTION, that is 40 long character, and the table contains just one row:

Using position to in a data structure array

Update

This is a better way to sort a data structure array using an update to the SORTA operation code.

 

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Any of you who have followed this blog for any amount of time are aware that I am proponent of using multiple row fetches in SQL to load data into a data structure array, which I will then use to load something like a subfile. In all the examples I have given in the past have been for files/tables that could contain many records/rows more than could be loaded into a load all subfile.

The slowest part of any program is loading data from the file/table. Using a multiple row fetch makes this many times faster by reducing the number of disk I/O to get my desired amount of data, versus getting one record at a time as I would need to do if I was using RPG to read the file/table. Every time I reload the subfile it is slow as I have to get the data from disk. This is especially true if I have a "Position to" field on my display file. If I am using a large file I have to reload the subfile every time the position to field is changed.

Using a trigger to prevent the deleting of records

The idea for this post came from a question I was asked about ways to stop a programmer from deleting records from a file using the STRSQL command. I thought this would be a good reason to use a combination of two solutions I have written about before.

My first thought was to use a validation trigger. Validation triggers must be executed before the insert, update, or delete occurs. That way I can determine if the STRSQL program was used, and if it was return an error code to the calling program.

Validation programs can be written in any language, and I have written them in both RPG and SQL. In this scenario I will be writing the trigger in SQL as, in my opinion, it is easier to write and, more importantly, easier for someone else to understand what is going on.

Find String PDM to an outfile

We have all had those requests from our superiors: "Where is insert-name-here file used?"

There are tools from third parties that will give me this information. I have used some of them, and found that they missed some objects. I always combine the information these tools provide me with a scan of the members in the source files in the production library list. I use the Find String PDM command, FNDSTRPDM, to search for the string of information I want. Most people who use this command use it to produce a printed list of the source members it finds. While that may be OK if there are just a few libraries and source members, I work in an environment where there are 25 libraries in the production library list and many of these libraries contain multiple source files. I do not want to have to copy information from all of the generated spool files into a physical file that I can share with others, that would be too much work.

Looking at the help for the FNDSTRPDM I had a eureka moment, that would give me a way to write the name of the source member to an output file.