IT Management

For mainframe folks, this means realizing that this is, indeed, a brave new world and that there isn’t always a wellknown set of time-tested procedures for a given situation. The Linux group must recognize that more than 30 years of mainframe operations have resulted in best practices worth examining. Systems programming isn’t a matter of doing things the way you like to do them, or the way that’s most convenient. It’s doing things right, where “right” is defined by those who have come before, and have scars from past mistakes to prove it.

Another area of conflict lies in documentation. IBM has, for decades, produced the best documentation in the computing world. IBM documentation is generally so complete and coherent that third-party books on IBM topics are relatively rare. Linux folks, on the other hand, are used to having three levels of documentation:

  • How-to documents written by users who have fought the same battles before
  • Books they can buy at any bookstore
  • The source code itself (typically written in C).

So, when Linux users are first exposed to the mainframe, their first reaction often is, “Where’s the documentation?” They find few how-to materials. Then they visit Barnes & Noble and don’t find any books. If they even have access to VM source, they find that it’s written in Assembler, with which they’re unfamiliar! No wonder they’re frustrated. Having paper manuals handy and files in Adobe Acrobat PDF is essential for helping folks learn to navigate the IBM documentation.

The mainframe team is often surprised at the poor quality of Linux documentation. Books accompanying commercial Linux distributions are often wildly incomplete and poorly indexed.

Internet sites such as SlashDot, LinuxVM, LinuxDoc, and IBM’s VM and Linux on zSeries Resources pages can help answer questions and resolve specific problems. The Linux-390 mailing list, hosted by Marist College, is also helpful. IBM and other vendors offer classes on VM and Linux on zSeries. A more economical choice is attending SHARE, the national user group for IBM users. SHARE meets twice annually, each meeting offering a full week of sessions on various topics. Refer to the resources section for more details.

Installations with separate networking groups and mainframe groups often encounter problems integrating the Linux guests with the rest of the network. These are not technical issues, and can be overcome with effort on both sides. Networking folks are used to the mainframe being a single host. With Linux on the mainframe, there are suddenly whole networks “hiding” inside the zSeries black box. Since the networking folks cannot see or manipulate the cables, routers, etc., they’re often uncomfortable with this situation.

This can lead to difficulties setting up guests. External routers must be reconfigured to add new routes; traffic over the OSA or other real hardware connecting the mainframe to the LAN may increase dramatically, etc. As with any networking project, it helps to draw a diagram. This lets the network group see that there isn’t anything dramatically new. The new LANs are inside the box and may come and go without external intervention. It’s helpful to show the network team the output of VM NETSTAT and CP QUERY LAN commands, so they can see that it’s similar to what they’re used to.

Mainframe Linu x in Action

So how many organizations have worked through the cultural and technical issues, and migrated important applications to Linux on zSeries? Numbers are difficult to pinpoint. Some companies are reluctant to share information because they feel they’ve gained competitive advantage and don’t want competitors to follow them.

Linux on zSeries success stories include:

  • Winnebago Industries, which migrated its corporate mail system
  • Korean Airlines, which uses Linux on zSeries for its flight schedule inquiry system, revenue accounting system, and other strategic applications for maintenance and customer service
  • Boscov’s Department Stores, the fourth largest retailer in the U.S., which runs large parts of its back-end operations on it.

Universities, a traditional bastion of both VM and Linux, are also heavily using Linux on zSeries. Marist College uses it for classes. Each student can be given a virtual machine, and can build and modify the Linux environment without affecting others.

Several financial organizations on Wall Street are known to be running quiet but extensive pilot programs, as are some large insurance companies. A big surprise is that the expected early uses of mainframe Linux were for infrastructure applications: Web, file, and print serving, e-mail, etc. While these applications are frequently seen, usage has quickly expanded to include business applications such as WebLogic, WebSphere, and DB2 Connect. This suggests customers are realizing the value of Linux on zSeries even faster than Linux fans hoped!


With Linux for zSeries and System/ 390, VM was indeed reborn, although its new role — hosting multiple copies of another OS — is strikingly similar to that for which it was first created. No longer is VM the “poor cousin” to its MVS-derived brethren, with hardware support lagging by months or years. In fact, VM has supported the latest IBM hardware advances ahead of z/OS!

Linux on the mainframe forces mainframe, distributed systems, and networking teams to converge. As the groups learn from each other, companies will realize value far beyond that which Linux itself brings.

Linux is young and dynamic. Employees are finding something new to learn and enhancing their value while adding to their companies’ bottom lines. Linux is a part of every IT installation’s future. With z/VM’s added value, Linux on zSeries is likely to be a part of the most successful companies’ futures! Z

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