Introduction

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

Oracle Tuxedo Application Rehosting Workbench 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

Oracle Tuxedo Application Rehosting Workbench 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:

•	Plan the project, setting the general requirements and planning the target architecture options.

•	Prepare the assets to be converted and install and configure the target environment.

•	Convert the assets.

•	Integrate the assets in the target environment.

These functions may be performed iteratively, typically a project consists of the following phases:

•	Setting project strategy.

•	Assessment study.

•	Pilot project.

•	Implementation.

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:

1.	A current production source environment for the assets to be converted.

2.	A test source environment for storing and isolating the operations extracted from the production environment and for creating a test database.

3.	A test target environment for running, tuning and testing the converted assets.

4.	An integration target environment, which is used to host all activities such as integration, operations migration or pre switch-over processing.

5.	A production target environment for the converted and tested assets.

Table 1‑1 Project environments

Environments	Production	Integration	Test
Source	Production Source		Test Source
Target	Production Target	Integration target	Test Target

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

Phase	Migration Steps	Test Step	Environment	Language/ Data
PROJECT MANAGEMENT	Project Definition
PRE-CONVERSION	Asset Generation		Source Production to Source Test	Both
	Asset Cataloging Asset Rationalization (if necessary)		Source Test	Language
	External Specifications Architecture Development		Planning and preparation for Target environments
	Data Conversion		Source Test to Target test	Data
TEST PREPARATION		Test Engineering Test Preparation Test Tooling	Source Test	Both
PILOT	Pilot Set Conversion	Pilot Set Testing	Target Test	Language
BALANCE	Balance Conversion	Balance Testing	Target Test	Language
INTEGRATION	System Integration Operations Migration	System Testing Operations Testing	Target Test to Target Integration	Both
SWITCH-OVER	Maintenance Conversion Maintenance Conversion Testing	Maintenance Testing Dry Runs	Target Test	Both
	Switch-Over		Target Integration to Target Production
EDUCATION	Education And Training

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

Oracle Tuxedo Application Rehosting Workbench 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

Oracle Tuxedo Application Rehosting Workbench 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