Time and time again I hear people talk about how companies are getting rid of their ‘legacy’ systems. What are these systems and what makes them classified as such? And what are they replacing them with?
Thanks.
http://www.hyperdictionary.com/computing/legacy+system
It’s basically hardware/software that a company continues to use because it still serves the intended purpose even if it isn’t state of the art. A lot of these system survive long past their intended lifetime because the cost of replacement is greater than the cost of continued maintenance.
In general, legacy systems are programs that run on older or unsupported computers/operating systems. Usually they are talking about COBOL applications running on old IBM mainframe computers, but the term can also be applied to programs written for an MS-DOS or other environment.
The key to replacing a ‘legacy’ system with something else is that it would be more difficult/expensive to fix the existing system than to throw it out and start over.
In the case of retail hardware, it’s the piece of equipment you bought a month ago that you can’t find drivers for anymore. 
It’s basically a trendy term that sales people use to disparage (without insulting) a customer’s existing system. Instead of saying “your existing system is a piece of outdated junk,” they say it is a “legacy system.”
Like micco said.
The only thing I’d add is that they’re the workhorse systems that you can’t justify replacing (yet), but that you’re not going to spend a lot of time and money updating. Software salespeople know this, so they spend a lot of time and energy demonstrating how their product will integrate with, thus “protecting your investment in”, your legacy systems.
It mostly refers to ISA cards but also serial ports and parallel ports. These are the technologies that are being replaced by newer/faster/smaller ones. Basically, old standards that companies aren’t making any new products for.
Anything can become a legacy system. Something that’s state-of-the-art now will be a legacy system in n years (where n is a number asymptotically approaching 0 roughly in accordance with Moore’s Law) if enough people invest in it now and don’t see a good enough reason to invalidate that investment when it becomes obsolete. There are some systems now that can be said to be what is usually meant by the phrase as it stands, but that will change as the technology advances.
As an interesting example of legacy systems in current use, the San Francisco BART is using (or was using last time I heard) DEC PDP-8 minicomputers to control their systems. PDP-8s were state-of-the-art in the 1960s and are currently antiques by most modern senses of the term, roughly equivalent to flintlocks or sail-driven wooden ships. You’ll never see a new PDP-8 coming up for sale, but there is nothing saying the existing ones can’t be repaired and used indefinitely.
Except for the fact that PDP-8 parts are getting harder and harder to come by.
One of these days, I’d love to see BART’s IT department. I have visions of VT-52 terminals alongside Bridgeport milling machines.
The VTs are there to talk to the PDPs and the Bridgeports are to make new parts for the PDPs. That can’t be too far of an exaggeration - their AFC (Automated Fare Collection) techs look like mobile blacksmiths. They trundle along all day long station to station with carts full of curious mechanical bits and parts to patch the elderly computerized faregates and ticket vending machines into something resembling operating condition.
They’ve been working on replacing the 30 year old gates (talk about legacy equipment!) with new ones that include reader pads for the not-quite-working “one card for all transit” system that uses an RFID card, but still, it’s mechanical stuff that gets a lot of abuse.
Where I’m at, the “biggie” legacy system runs on Tandem computers, which are becoming a bit of a challenge to find parts for. It doesn’t help that Tandem was re-absorbed by Compaq (Like HandSpring came out of Palm, Tandem was started by some Compaq people) and Compaq was gobbled up by HP. HP seems more concerned with selling printers and semi-reliable home PCs than maintaining their high-end server lines.
No matter to us. The system has been re-built and in a couple months, we’ll unplug the Tandems and have it all running on a Sun Enterprise 15K machine. For over $2.5 million, this thing better last us a couple decades! 
My little legacy system uses IBM 3151 terminals that are in IBM 3101 emulation mode. Every piece of equipment we have emulates an older piece that emulated the original.
Ironically, what’s forcing us to scrap the system is that we built the latest hardware platform around the latest generation communication card, which has now been discontinued!
When you’re talking about in-house software, “legacy” can refer to systems that were developed by programmers who are no longer with the company. The current programming staff has inherited it from their predecessors, so it’s a legacy.
Huh? I thought Tandem was around before Compaq…
Ersh… You’re right. Tandem started in 1975 and Compaq was hatched in 1982. :smack: But I wouldn’t be surprised if there was more than a little mingling of staff through the years.