Mainframes are computers

At their core, mainframes are high-performance computers with large memory (RAM) and processors that process billions of simple calculations and transactions in real-time.

The mainframe is critical to commercial databases, transaction servers and applications that require high reliability, scalability, compatibility and security – the core design values of the mainframe.

The IBM Z® mainframe supports multiple operating systems, including Linux, z/OS®, z/VSE®, z/VM® and zTPF, and many open source packages, including the Open Mainframe Project.

Mainframe stats


Mainframes have 99.999% uptime, or less than 1 minute of unplanned downtime per server per year. (1) The mainframe’s “Mean Time Between Failure” is measured in decades. (2)


IBM z14™ mainframes seamlessly encrypts 100% of application, cloud service and database data. It has 8.5 times the interception level of alternative platform solutions with 81% less effort. (3)


Run up to 8,000 virtual machines on a single server with 160 I/O cards 320 I/O channels. A single mainframe is equivalent to approximately 1,500 x86 servers. (4)


IBM z14 has 14 nanometer cores, 170 configurable processors, 6.8GB of cache memory, 32TB of main memory and 10 cores per chip to process up to 30 billion transactions daily.

Who uses mainframes?

Organizations that need the core quality of services that mainframes provide –  highly secure, large scale transactions in real-time with 24x7 availability – rely on the mainframe.

Data centers rely on mainframes to handle surges in traffic. The mainframe scales up in seconds by turning on more capacity. Other platforms scale out, which requires system admins to add more physical servers.

Companies that process bank and credit card transactions, airline reservations, retail purchases, blockchains, and even driver’s licenses use mainframes to run high-volume transactions in milliseconds and protect sensitive data.

You use a mainframe. Behind the scenes of so much of your everyday technology is a mainframe. See how long you can last without a mainframe.

Mainframes are a big deal

Today’s mainframes are powerful, but not as large as their old nickname, Big Iron, implies. In fact, the IBM z14 is the same width as other servers – 19 inches – and can slide right into any data center, fitting in the space of 2 floor tiles. What makes a server a mainframe is not its size, but how it is designed to perform. 

Big for business

The mainframe is used by 44 out of the top 50 worldwide banks, 10 out of the top 10 insurers and 18 out of the top 25 retailers.

Big for clients

92% of clients predict long-term viability of the mainframe 59% see increases in transaction volumes and 48% use DevOps practices.

Big for careers

Mainframe developers are in demand and starting salaries are higher than most other college graduates.

Mainframes have a history of technology breakthroughs


From the beginning, the mainframe was built to take businesses to the next level.


New technologies on the mainframe made centralization possible.


Mainframe capabilities like virtualization made the cloud possible.

Pervasive encryption

Mainframes continue to innovate to remain the most secure platform.

Meet some mainframers

Luisa Martinez

Luisa tries something new – developing on the mainframe.

Alex Stuart

Alex describes how he “is splunking the mainframe.”

Meghan McGrath

Meghan shares how she helped bring 100% encryption to the mainframe.

Go deeper

Create an app

Use these tutorials to create an app that accesses the mainframe.

Get hands-on learning

Use the learning system to go from novice to a skilled mainframer.

Try software

Try mainframe software at zero cost, and with no installation required.