The Legacy Directory - Automated Inventory

Software Migration Using The Legacy Directory

The Legacy Directory is a tool that automatically documents existing computer systems. The ability of The Legacy Directory to produce an as-is fully cross-referenced directory of the existing production environment, as opposed to a list of the application elements that exist in a production library, ensures that should the decision be taken to enhance, retire, convert or migrate a portion of the current environment, the project teams will know exactly what, or what not, is to be converted and have a clear idea of where the boundaries of the application are.

In most large mainframe shops, systems are made up of components from potentially the last four decades of the twentieth century. From the early days of enterprise computing, with its emphasis on speed (and the use of 2nd generation computer languages and flat files) through to today with object oriented technologies using the latest RDBMS products, most systems are a combination of the "Latest thing" from each decade, whether they are programming languages, relational databases, productivity tools or RAD methods. The effect has been to produce a set of systems with a "poi-pourri" of application object types that work on corporate databases that interact at the edges with other systems and providing the business with its front and back office systems that may, or may not, still be mainframe based.

It is little wonder that with the maturation of *nix/Windows in the commercial world, many companies are looking to off load their existing systems and start afresh with server based technologies. Many organisations perceive huge cost savings in moving from z/OS (whether on Intel based servers or hosted on IBM mainframes) and a growing number of commercial packages are becoming available on the new platforms. Other companies are just planning to exploit the new technology in a way that can been seen as a continuum from the Assembler based systems of the 1970's to the Object Oriented systems currently being programmed in the second decade of the 21st Century.

There are, basically, two ways in which to migrate an organisations computer systems. The first involves installing and configuring an over-arching series of systems that will completely replace the existing environment. This could be categorised as the “Big Bang” approach. The other is a staged series of developments that will, over time, replace the existing mainframe systems with new functionality that will have, for the moment, to interface in one form or another, with applications that still exist on the mainframe. We at Legacy Software believe that “Big Bang” approaches have their place but in mission critical environments, a phased development with existing systems kept going until they can be safely decommissioned is both safer and, in time, less costly to the organisation.

We will concentrate here on the phased migration of systems and how The Legacy Directory can assist in both aiding the redevelopment of systems while ensuring that the interfaces between new and old are maintained.

One of the key requirements in ensuring that interface development is kept to a minimum is to understand what does, and more importantly does not, constitute the existing system.

The Legacy Directory will document your production system In the graphic to the right, the "cloud" can be seen as the totality of the application objects that are stored in an organisation's libraries (whether PDS's or library control systems). Only a proportion of those object are actually used. One of our clients put this very eloquently when he said that "We knew that 50% of our code was redundant, we just didn't know which 50%".

The key to migrating systems in a orderly fashion is to first identify what exactly constitutes that system. This involves analysing the existing code to ensure that it is actually used. This can, in today's integrated environment take quite some time. Even worse, once a production systems “edges” have been established, it is critical to know how those systems interact with other computer systems and it is these interfaces that will need to be taken good care of in a phased move to a new environment.

What is needed is the ability to automatically establish the boundaries of a computer system and document exactly where, and how other systems interact with it. This is exactly what The Legacy Directory has been designed to do. To automatically establish the components used in the production environment, highlight redundant elements, show where code has been lost (the latter being of critical importance if business rules are being extracted from the current systems in order to re-engineer them to a new platform) and draw boundaries around application elements to show both the formal and informal (shared) components of a system.

The Legacy Directory is unique in that it can automatically detect the type of objects to be scanned, (be they COBOL or PL/1 programs, DB2 or IMS database definitions, JCL, CICS information etc.) and then automatically scan them to establish, to a user specified level of information, a fully populated directory (repository) of system information which can immediately be accessed by project teams. The Legacy Directory provides easy-to-use techniques to establish the boundaries of an application system and, as a by-product of its optimised loading process, a list of orphan elements (those elements that are not used by anything) and missing code (items which have not been scanned or are lost) or are in as yet undiscovered libraries.

The Legacy Directory can be used to provide a number of different levels of information. The most widely used is "The Enterprise View", a directory that shows how all the system components relate to each other. Using the facilities of The Legacy Directory, it is immediately possible to isolate the actual components of a legacy system, as opposed to the components that were, at one time, active, but are no longer used.

The Legacy Directory can also show the components that are shared with other application systems. These could be code, data or process components (such as jobs) and it is these informal interface components that will need to be maintained through the migration process. The Legacy Directory helps you to keep track of where the formal and informal boundaries of a system are and ensure that developers and maintenance staff are aware of what really is going on in the production environment.

In summary, The Legacy Directory automatically provides an as-is picture of the existing application environment and provides the IT department with an easy method of establishing what needs to be maintained, what can safely be de-commissioned and what the effects of a projected change in the production environment would be. For more information on The Legacy Directory, contact Legacy Software today