Saturday, 25 June 2011

What’s a mainframe, Daddy?

After years of sliding my security card in the lock and entering the machine room/data centre and seeing the mainframes in there change from Sci-Fi-style boxes with flashing lights to more mundane-looking boxes. From seeing simple DASD with less capacity than the memory stick in this laptop be replaced with cache controllers and more sophisticated data storage devices. It always seemed that there were plenty of mainframes around and any normal person (me) was constantly being offered tours round installations. So it comes as a bit of a shock when a youngster clearly has no idea what a mainframe looks like or what it does!

OK, no-one may have actually said those words as such, but that was the message. Plus, I was with some friends on Saturday when the conversation turned to discussing what use a mainframe was in this day and age! As Arcati Director, Mark Lillycrop, so eloquently put it recently, mainframes are thought of as ‘your dad’s technology’. Most of the people I was chatting to felt that mainframes were relics of the past and anything they can do, a few servers could do just as well!

So for many of us mainframe verterans, our job is to get out there and spread the word. We need to tell people exactly what a mainframe is, what it can do, and how people are interacting with them all the time, but don’t realise it. That way, the new generation of youngsters that are beginning to get access to mainframe technology at universities and elsewhere will arrive with a knowledge of what mainframes can do, and why working with them can be so enjoyable.

So let’s just start with the absolute beginner’s guide to mainframes. They are computers – just like your laptop – except that over the years they faced and solved all the problems about back-ups and restores, security, and high-speed data access. They have been around for a long time – which is a good thing because lots of people have moved the technology forward. They allow millions of users controlled access to information – allowing them to create, modify, and save data from almost any data entry device you can think of, including browsers.

Mainframes have been virtualized since the 1980s, and some of the software first saw the light of day in the 1960s. Most Windows data centres have only been virtualizing for the past five years! It’s true that laptops etc are everywhere – in your home, at work, etc – but mainframes are working away in the background. Everytime you take money from an ATM (cash machine) your bank is running a transaction on a mainframe. And it is banks and large financial institutions that use mainframes. And they do it because of the reliability. They do it because, should there be an outage, they can recover back to almost the last second before they went down. Almost no transactions are lost. And as a bank customer, I like that. Lots of non-mainframe-using sites think they are doing quite well if they can recover data back to last night! You see the difference in scale here.

Mainframes run an operating system (z/OS, but could be z/VM or z/VSE) and on top of that are a number of subsystems – you might think of them as apps (but big ones!). These subsystems include CICS and IMS. Now, both of these have been being developed since the 1960s and provide ways of accessing data very quickly and securely. They allow users to fill in virtual forms. And they store data in a way that means it can be accessed very quickly.

Another ‘app’ you may have heard of is DB2. DB2 is a comparative youngster, having arrived in the 1980s. It stores data in a ‘relational’ way rather than the more traditional ‘hierarchical’ way. DB2 is a database that can exist on Windows machines as well as mainframes (and many devices in between).

Mainframes can also run Linux (z/Linux) and all the Linux applications. That makes them very cost-effective replacements for sites with numerous ageing Linux servers. Linux has been available on mainframes for just over 10 years.

And there’s plenty of software available to control all aspects of this mainframe behemoth. And you can link them together at different sites in different countries round the globe.

So if anyone asks you what’s a mainframe, you can tell them that it’s the most successful server architecture ever devised and it’s all around them doing important work.

1 comment:

Exeter.Grumpy said...

Trevor, just for the sake of completeness:

"Mainframes run an operating system (z/OS, but could be z/VM or z/VSE, or even z/TPF)"