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Technology: Migration – Legacy Systems To 4GL Technology - Part I

Vidya Jagannathan

Migration – legacy Systems to 4GL Technology

Legacy applications are frequently large, monolithic and difficult to modify, and scrapping or replacing them often means reengineering an organization’s business processes (workflow) as well. Legacy migration is about retaining and extending the value of the legacy investment through migration to new platforms.

Re-implementing applications on new platforms in this way can reduce operational costs, and the additional capabilities of new technologies can provide access to valuable functions such as Web Access to the client. Once migration is complete the applications can be aligned more closely to current and future business needs through the addition of new functionality to the migrated application.

In short, the legacy migration process can be a cost-effective and accurate way to preserve legacy investments and thereby avoid the costs and business impact of migration to entirely new software.

The goal of legacy migration is to retain the value of the legacy asset (which has been built and stabilized over a period of time) on the new platform. In practice this migration can take several forms. For example, it might involve translation of the source code, re-architecting (Client server to Multi-tier, which is common application deployment platform) or some level of re-use of existing code plus a Web-to-host capability to provide the customer access required by the business.

Migration - Business Driver
Developments in Legacy Migration provide an opportunity for the business to review its legacy portfolio. To migrate or replace, to scrap or re-invest (re-write the whole application). These drivers are contrasted in the following diagram, suggesting that there can be quite a variation in the value that the business will be looking for from a migration.

In the above architecture the presentation logic and the business logic is tightly coupled together, which interacts with the common database.

Why Migrate, Why not Re-write?

Software experts use the terms migration and conversion interchangeably. For simpler understanding we shall use migration through out this document. This activity of migration involves the change of either the programming language or the data management technology or may be in certain cases both. In most of the cases, both are not changed simultaneously. The hardware, operating system and related system calls are not changed. Further more the design of the application; the programming logic and its structure are retained.

Similarly, in the case of data management technology, the existing physical data model is retained as far as possible. Data structures and data elements are retained as they are. 

The major reasons why the application needs to be migrated and some overall benefits of migration. Business today urges openness and direct access in terms of its manifest to targeted business world through cutting-edge technology. Thus, the new role of existing systems today is to provide the business capabilities on open and distributed technological architecture for global access of information. Other benefits and migration tools will be discussed in the next issue.

(Vidya received her MA in Communications from Madras University. She started SolveIT in 2003 to develop the tool to support migration. She can be reached at vidya@solveitcorp.com. )

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