Book Image

Modernizing Legacy Applications to Microsoft Azure

By : Steve Read, Larry Mead
Book Image

Modernizing Legacy Applications to Microsoft Azure

By: Steve Read, Larry Mead

Overview of this book

Organizations have varying circumstances, objectives, and prerequisites when contemplating a hyper-scale cloud solution transformation to a platform such as Azure. Modernizing Legacy Applications to Microsoft Azure uncovers potential scenarios and provides choices, methodologies, techniques, and prospective possibilities for transitioning from legacy applications to the Microsoft Azure environment. You’ll start by understanding the legacy systems and the main concerns regarding migration. Then, you’ll investigate why distributed architectures are compelling and the various components of the Azure platform needed during migration. After that, you’ll explore the approaches to modernizing legacy applications and the Rs of modernizing (i.e., rehost, refactor, rearchitect, and retire). You’ll also learn about integration approaches and potential pitfalls. By the end of this book, you’ll be well equipped to modernize your legacy workloads while being aware of pitfalls and best practices.
Table of Contents (18 chapters)
1
Part 1: Legacy Estate Options
3
Chapter 2: Strategies for Modernizing IBM and Unisys Mainframes
6
Part 2: Architecture Options
10
Part 3: Azure Deployment and Future Considerations

Current legacy hardware and operating system

Many people think of mainframes when the term legacy estate is used. However, the term mainframe does not have the same meaning for all people. Additionally, there are non-mainframe systems that can either make up or surround a legacy estate. This section will focus on four types of legacy estates:

  • IBM and Unisys mainframes
  • IBM midrange
  • Enterprise Unix
  • Other legacy estates

IBM and Unisys mainframes

IBM mainframes have been around for over 50 years and have the largest share of the mainframe market. The current version is called the z series. Several operating systems can run on z hardware, including z/OS, z/VSE, z/TPF, and z/VM. Currently, IBM mainframes can also run Linux and specialty engines such as the z Integrated Information Processor (zIIP) and Integrated Facility for Linux (IFL). The most common operating environment we see is z/OS, which might also include zIIPs and IFLs in the same environment. This will be the type of IBM mainframe environment we will look at in this book for modernizing to Azure.

If you do have an IBM mainframe estate running z/OS, there are several other factors that you need to take into account before proceeding with an Azure cloud modernization. These include the mainframe size, features in use, and Service Level Agreements (SLAs). All of these factors need to be considered when modernizing to Azure.

The second largest mainframe market share belongs to Unisys. As with IBM mainframes, Unisys mainframes come in multiple versions. These include Libra (MCP) and Dorado (2200). To understand the differences, it is important to look at their history. Unisys is the result of a merger of two companies, Burroughs and Sperry. Libra comes from the Burroughs lineage. Dorado comes from the Sperry lineage. Keep in mind these are separate operating systems and require different modernization strategies.

As with IBM mainframes, you also need to take into account sizing, features, and SLAs.

IBM Midrange

For this book, we will consider IBM midrange systems to be POWER-based hardware that runs the iSeries OS. The IBM iSeries platform has been in existence for over 30 years and has included systems such as AS/400, System 36, and System 38. Many users of the iSeries platform also run mainframe systems. However, the iSeries is a distinct operating environment versus the IBM z series. As the name implies, midrange systems are typically smaller than mainframes. These systems may run mission-critical applications that require high performance. The iSeries operating system is tightly integrated with the POWER hardware to provide this high level of performance. Unlike the z systems, the iSeries is the only operating system for midrange. There are multiple versions of the iSeries in use today. But these share a common ancestry.

The POWER hardware can also run a Unix variant (AIX). This will be discussed separately in Chapter 3. Sizing, features, and SLAs are also factors for modernizing the iSeries.

Enterprise Unix

While there are several versions of Unix, for this book, we will concentrate on AIX, Solaris, and HP-UX. Unix systems are very different than mainframe and midrange environments. Unix systems were one of the first operating system environments that promised the option of Open Systems. However, as it turns out, the Unix of Open Systems meant the operating system could run on multiple hardware platforms, not that applications developed for one platform could run without modification on another platform. Unix systems are still widely used in several systems. However, each major variant requires a different approach.

IBM AIX systems on POWER hardware are widely used and provide high performance and availability. Solaris is also widely used. Solaris can currently run on x86 but also continues to run on Sparc hardware. HP-UX is still available on HP Epic (Itanium)-based hardware. Enterprise Unix systems were developed over 30 years ago but are more closely related to today’s distributed and cloud systems. Enterprise Unix still has some legacy problems such as proprietary hardware/OS and agility.

Other legacy estates

Just to cover other legacy environments, there are several legacy operating systems and hardware. These include other z operating systems, such as z/TPF and z/VSE, other midrange systems such as Dec VAX, other mainframes such as Bull and NCR, and specialized operating systems such as HPE NonStop. While we will not go into detail about moving these environments to Azure, here are some options you can use for these environments that are similar to the areas we will cover:

  • z/TPF: Similar to approaches for Enterprise Unix, but specialized throughput and availability
  • z/VSE: Similar to approaches for z/OS
  • VAX: Similar approach to Enterprise Unix
  • Bull and NCR: Similar to the approach for Unisys
  • HPE NonStop: Similar to z/OS, but with special attention to redundancy

These operating systems provide scale-up functionality similar to IBM and Unisys mainframes, and applications on these systems are typically written in legacy languages such as COBOL. This chapter will reference these systems in sections where features provided by them are discussed.