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This chapter covers the following topics:
What is Rehosting?
Rehosting Projects
What is Rehosting?
Rehosting is a way to preserve the expensive investments in business logic and business data trapped in proprietary hardware and software, while opening paths to future modernization by moving to an open and more extensible architecture.
Product Overview
Refine for Z/OS Replatforming package provides automated migration tools to enable customers to replatform COBOL, JCL, DB2, VSAM files and related assets from an IBM DB2 mainframe environment to a UNIX environment with a Tuxedo transaction processor and an Oracle database.
Rehosting Projects
Refine for Z/OS Replatforming and Oracle Tuxedo Application Runtime for CICS and Batch are used within the context of a rehosting project. The process guide gives a global view of rehosting and the use of the conversion and runtime tools in this process. A rehosting project requires the creation of specific test, integration and production environments. The different functions of a rehosting project are typically:
These functions may be performed iteratively, typically a project consists of the following phases:
Each of these phases is made up of different steps, the results of these steps may be tested and the steps reiterated as necessary.
Projects, Phases and Steps
Rehosting is performed within a project organized into phases and steps. Each step produces one or more deliverables. In parallel to the different steps of the rehosting project are a parallel series of test steps that validate the different phases of the project.
A project concerns different people who have different roles and responsibilities within the project. A project is carried out within an environment and it is impossible to describe the different phases and steps of a project without first describing the environment in which they need to be performed.
Project Environment
There are five clearly distinct environments necessary to carry-out a rehosting project. These include two source (pre-migration) environments and three target (post-migration) environments as described below:
A current production source environment for the assets to be converted.
A test source environment for storing and isolating the operations extracted from the production environment and for creating a test database.
A test target environment for running, tuning and testing the converted assets.
An integration target environment, which is used to host all activities such as integration, operations migration or pre switch-over processing.
A production target environment for the converted and tested assets.
Depending on your needs, there may be several occurrences of the same platform to allow teams to work in parallel within the same project.
Project Phase Overview
A project is divided into different phases of work, producing clear deliverables that are validated before proceeding to the next phase of the project. These phases are as follows
Table 1‑2 Project Phases
Graphically, the different phases may be grouped as shown below:
Figure 1‑1 Project Phases and Processes
Overview of Using the Product in a Project
Refine for Z/OS Replatforming is used for converting and integrating program components and data. The following diagram shows the use of the program components, and how they are used to prepare source files for migrating to different environments.
Figure 1‑2 Language Migration
Refine for Z/OS Replatforming components are used to convert assets, enabling them after post-conversion adjustments to be moved from the from the source test environment to the target test environment.
Oracle Tuxedo Application Runtime for CICS and Batch components are used to integrate the converted assets after testing and integration preparation on the target test environment. The COBOL programs, JCL and associated components are integrated with the UNIX, Oracle database and Tuxedo transaction environments. These components are tested to work with the batch and CICS components produced during the conversion process.
Figure 1‑3 Data Migration
The assets to be migrated are generated and moved to the source test machine. The migrated assets are then converted and moved to a target test machine containing an Oracle database. After testing, the data is moved to an integration environment where rehosting tools are integrated with the programs to test their quality and performance using the converted data. When switchover occurs the latest data is converted directly from the source production environment to the target production environment.
Figure 1‑4 Migration Architecture

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