Built on the principles of Mass, Automated, and Repetitive conversion described in “Methodology”, the conversion is organized in seven phases:

Application Inventory


Installation and Custom Modification of Conversion Software

First Trial Conversion

z/OS Tests and Repetitive Trial Conversions

Actual Conversion and Switchover

Assisted z/OS Operations

Phase 1: Application Inventory

As a preliminary step for the VSE to z/OS conversion, the application inventory must be collected and verified for completeness and consistency.  Clean application inventory libraries are required to properly identify the conversion requirements and develop quality conversion specifications, the key to a smooth and efficient project.  The application inventory tasks include:

  • Developing an inventory transfer procedure
  • Loading the conversion inventory into libraries *
  • Executing the ConvTek inventory validation software *
  • Identifying missing or un-referenced elements in the conversion inventory *
  • Resolving the missing and un-referenced elements in the conversion inventory *

(*)  Usually up to four iterations

Phase 2: Specifications

The project-specific conversion requirements are determined and documented during the specifications phase.  The specifications tasks include:

  • Developing a project plan
  • Orienting the conversion project team to the conversion approach and to the project plan
  • Installing the conversion software and performing a preliminary tailoring to local conditions
  • Studying the VSE source production environment
  • Defining the z/OS target production environment, including z/OS standards
  • Performing a pilot conversion of a subset of the conversion inventory before custom modifying the conversion software
  • Identifying conversion issues and source code positioning activities
  • Designing automated conversion solutions, based on custom modification of the conversion software, or development of additional ad-hoc conversion software
  • Meeting with technical representatives of VSE and z/OS operations, technical support, and applications development

Phase 3: Installation and Custom Modification of Conversion Software

The conversion software is installed, tailored, and custom modified to handle the conversion requirements, as defined during the specifications phase.  The Custom Modifications tasks include:

  • Tailoring and custom modifying conversion software through installation options and exit routines according to the conversion specifications
  • Performing a pilot conversion of a subset of the conversion inventory after having custom modified the conversion software
  • Auditing the messages and z/OS material (source code and JCL) produced by the pilot conversion
  • Performing technical tests on a representative sample

Phase 4: First Trial Conversion

The first trial conversion and all following trial conversions simulate the actual (i.e. final) conversion.  The entire conversion inventory is converted to z/OS.  The trial conversions deliver z/OS programs, load modules, JCL streams, and files for test in the z/OS environment.  Problems encountered during the first trial conversion are used to identify and document additional conversion software custom modification requirements. Custom modification is refined accordingly.  The first trial conversion starts with a complete fresh supply of the VSE conversion inventory.  During the first trial conversion, VSE files needed for z/OS tests are migrated to z/OS.

Phase 5: z/OS Tests and Repetitive Trial Conversions

Jobs selected during the specifications phase, typically those scheduled to run within four weeks after the actual conversion and switchover, are tested in the z/OS environment.  z/OS tests require careful planning and organization, z/OS machine time and disk space, full access to VSE production procedures and documentation, availability of data and criteria to validate test results and direct participation of WHB.  Problems discovered during the z/OS tests are analyzed both in nature and in frequency.  Typical solutions for problems with multiple occurrences involve improvements to the automated mass conversion process (conversion software custom modification) followed by new trial mass conversions.

z/OS batch application tests include:

  • Sample (technical) tests: execution of a representative job sample
  • Application Acceptance and User Acceptance Tests:  job executions following the applications flows
  • Production Acceptance Tests:  replicate one day of VSE operations in z/OS

z/OS online application tests include:

  • Initialization (installation) tests:  start each transaction to verify that the initial screen comes up
  • Sample (technical) tests: execution of a representative transaction sample
  • Application Acceptance and User Acceptance Tests:  chained transactions following the application flows
  • Production Acceptance Tests:  in conjunction with batch production tests
  • Network and performance tests with actual connection to future end-users

Batch and online production tests are coordinated to test the integration of batch and online applications.  The products selected for z/OS operations (e.g. tape manager, job scheduler and report manager) are used for the batch functional and production tests in order to validate their installation and set-up.

The z/OS tests and repetitive trial conversions are organized into an interactive loop of tasks including:

  • Orientation to the test phase
  • Defining a test plan with scenarios for batch job scheduling and for execution of online transactions
  • Defining a procedure to verify batch and online test results
  • Executing online transactions
  • Preparing and executing batch jobs
  • Verifying and validating test results
  • Identifying and analyzing test exceptions
  • Applying short-term solutions to promptly resume the tests in progress
  • Reviewing the nature and frequency of test exceptions
  • Designing and developing permanent solutions based on the improvement of the automated mass conversion process
  • Refining conversion software custom modification
  • Supplying fresh copies of the conversion inventory for each new trial conversion
  • Performing trial mass conversions
  • Supplying new z/OS JCL and programs for test in z/OS
  • Migrating copies of VSE production files, needed for tests, to z/OS

The conversion project team meets regularly to review the progress and status of the z/OS tests.

Phase 6: Actual Conversion and Switchover

The actual conversion is the final mass conversion, starting with a final fresh supply of the entire conversion inventory.  Both actual conversion and switchover are performed within two to four weeks, with the actual conversion starting on a Monday, and the switchover being completed on a Sunday.  Production testing is used to validate the actual conversion before switchover.  A final supply of conversion inventory, a few days before switchover, is used to identify any late VSE change control and to carry it over to the converted z/OS application.

As opposed to trial conversions, the actual conversion is followed by a mass migration of all permanent VSE production data files to z/OS, which requires production outage during the weekend.  After the file migration, some selected jobs are executed and some online applications are started and verified in actual production mode.

During the month preceding the switchover, all parties participate in planning and preparation activities.  These activities produce the final file migration JCL streams and switchover task lists.

Phase 7: Assisted z/OS Operations

After switchover, the conversion team assists the initial z/OS production flow with problem solving until all daily, weekly and monthly production jobs have been executed successfully within the z/OS environment.