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Most computer systems running on an AS/400 use the embedded DB2 database - a well known and understood technology. Reports would be generated based on the tabl

Most computer systems running on an AS/400 use the embedded DB2 database - a well known and understood technology. Reports would be generated based on the tables, no different from an Oracle based stack. RPG code is fairly easy to understand as well. Any experienced auditor or consultant would be abe to understand the routines easily. Maybe more easily than a Perl or C stack. I'm no fan of AS/400 for many reasons, but complexity is not one of them.

kibwen 5y ago
I'll dispute that RPG is fairly easy to understand. It wasn't designed as a general-purpose language, it's more like an alternate universe proto-SQL that was twisted into a general-purpose role. With few historical precedents to base it on as of 1959, its designers were flying by the seat of their pants, and it will be expressly alien to any developer who came of age after the early 90s. It's also a product of its time; six-character identifiers, eight-character filenames, and don't get me started on the fixed format (when I describe this to my developer friends, their eyes bug out of their head). Maybe if we're talking exclusively about the modern C-inspired free format, but IME most RPG code was written well before RPG IV, and any company that eager to rewrite their code is going to have rewritten it in e.g. Java instead.
- ch_123 5y ago
  The System/3x family and RPG were designed for customers who were migrating off unit record equipment. Unit record equipment was "programmed" by wiring plug boards, and the unit record machine would filter, transform, collate (etc.) each card in a stack of input cards by applying the rules specified by the wiring of the plug board. With the fixed formatting and "program cycle", RPG was intended as a sort of skeumorph for technicians who would have been trained to "program" unit record equipment on a wiring diagram. (Contrast the wiring schematic here: http://www.righto.com/2017/04/1950s-tax-preparation-plugboard.html http://www.righto.com/2017/04/1950s-tax-preparation-plugboar... with an RPG template here: https://www.richard-banks.org/2014/01/a-little-nostalgia-with-wang-vs-and-rpg.html https://www.richard-banks.org/2014/01/a-little-nostalgia-wit...)
- bluepizza 5y ago
  > Maybe if we're talking exclusively about the modern C-inspired free format, but IME most RPG code was written well before RPG IV That's an excellent point. I meant free format code
russh 5y ago
Legacy RPG code is usually not easy to understand. Each line of code can be conditioned with a series of Boolean indicators leading to a simple looking but complex spaghetti code. One line of code may run if indicators 13, 23, and 90 are set and the next only if 56 is set followed by a line that runs if 13 and 90 are set. You could have 99 indicators plus reserved indicator per program. This leads to pearls of wisdom like “An indicator is like an atomic bomb, nice to have but not something you want to use.” And “if you solve the problem with an indicator, then you’ll have two problems.”
chasil 5y ago
The DB2 on the iSeries is not built from the same source code as mainframe DB2, which likewise is not built from the same source code as Linux/Windows DB2. These may be carefully engineered to be compatible at many levels, but they are not the same thing, as Oracle might be as it is compiled for its supported platforms.

kibwen 5y ago

I'll dispute that RPG is fairly easy to understand. It wasn't designed as a general-purpose language, it's more like an alternate universe proto-SQL that was twisted into a general-purpose role. With few historical precedents to base it on as of 1959, its designers were flying by the seat of their pants, and it will be expressly alien to any developer who came of age after the early 90s. It's also a product of its time; six-character identifiers, eight-character filenames, and don't get me started on the fixed format (when I describe this to my developer friends, their eyes bug out of their head). Maybe if we're talking exclusively about the modern C-inspired free format, but IME most RPG code was written well before RPG IV, and any company that eager to rewrite their code is going to have rewritten it in e.g. Java instead.

ch_123 5y ago
The System/3x family and RPG were designed for customers who were migrating off unit record equipment. Unit record equipment was "programmed" by wiring plug boards, and the unit record machine would filter, transform, collate (etc.) each card in a stack of input cards by applying the rules specified by the wiring of the plug board. With the fixed formatting and "program cycle", RPG was intended as a sort of skeumorph for technicians who would have been trained to "program" unit record equipment on a wiring diagram. (Contrast the wiring schematic here: http://www.righto.com/2017/04/1950s-tax-preparation-plugboard.html http://www.righto.com/2017/04/1950s-tax-preparation-plugboar... with an RPG template here: https://www.richard-banks.org/2014/01/a-little-nostalgia-with-wang-vs-and-rpg.html https://www.richard-banks.org/2014/01/a-little-nostalgia-wit...)
bluepizza 5y ago
> Maybe if we're talking exclusively about the modern C-inspired free format, but IME most RPG code was written well before RPG IV That's an excellent point. I meant free format code

russh 5y ago

Legacy RPG code is usually not easy to understand. Each line of code can be conditioned with a series of Boolean indicators leading to a simple looking but complex spaghetti code. One line of code may run if indicators 13, 23, and 90 are set and the next only if 56 is set followed by a line that runs if 13 and 90 are set. You could have 99 indicators plus reserved indicator per program. This leads to pearls of wisdom like “An indicator is like an atomic bomb, nice to have but not something you want to use.” And “if you solve the problem with an indicator, then you’ll have two problems.”

chasil 5y ago

The DB2 on the iSeries is not built from the same source code as mainframe DB2, which likewise is not built from the same source code as Linux/Windows DB2. These may be carefully engineered to be compatible at many levels, but they are not the same thing, as Oracle might be as it is compiled for its supported platforms.