A VM/VSE customer wants to implement WebSphere Application Server (WAS) on an existing zSeries server. On which operating environment should WAS best be implemented in this scenario?

Introduction / Context:
This question deals with platform selection for deploying WebSphere Application Server on a zSeries mainframe. A customer currently uses VM/VSE but wants to add an application server environment. IBM supports WebSphere on several operating systems, including z/OS and Linux on zSeries, and the choice affects flexibility, skills, and cost.

Given Data / Assumptions:

The hardware platform is an existing zSeries server.

The current customer environment includes VM/VSE.

The customer wants to implement WebSphere Application Server.

The question asks where WAS would best be implemented, not just where it is theoretically possible.

Concept / Approach:
Linux on zSeries is a popular platform for Java application servers such as WebSphere because it offers flexibility, uses widely known Linux skills, and takes advantage of zSeries reliability and virtualization. While WebSphere can also run on z/OS, Linux is often recommended when customers want a more open, distributed style environment or when they are adding new workloads beside existing VM/VSE systems.

Step-by-Step Solution:
1. Eliminate VSE because WAS is not typically hosted directly on that environment. 2. Consider z/OS, which can host WebSphere but may require additional skills and licensing suited for tightly integrated mainframe workloads. 3. Consider Linux on zSeries, which combines the robustness of the mainframe with the flexibility of Linux and strong support for WebSphere. 4. z/VM itself is a virtualization environment rather than a primary host for WAS, although it can host Linux guests. 5. Based on IBM positioning, Linux on zSeries is generally presented as the best environment in this mixed scenario.

Verification / Alternative check:
IBM solution guides for consolidating distributed workloads onto the mainframe commonly recommend Linux on zSeries for Java and WebSphere workloads, especially for customers transitioning from other platforms.

Why Other Options Are Wrong:
VSE is focused on batch and transaction processing and is not the mainstream platform for WebSphere Application Server.
z/VM provides virtualization for other guest operating systems but does not serve as the primary WebSphere target itself.
z/OS can run WebSphere but may not be the best choice for a VM/VSE customer introducing new open systems style workloads when Linux on zSeries is available.

Common Pitfalls:
Students sometimes overlook Linux on mainframe as a viable WebSphere platform. Another pitfall is confusing virtual machine monitors such as z/VM with guest operating systems. Proper design separates the virtualization layer from the operating systems that host application servers.

Final Answer:
WebSphere Application Server is best implemented on Linux on zSeries in this scenario.