Everyone complains about the legacy application systems environment. The state of affairs of the legacy application environment is so abysmal that many information system managers consider the legacy systems environment to be their number one problem. The legacy environment has been maintained to the point of being shopworn. The legacy systems environment reflects the business of yesterday. The legacy systems environment is built on technology best suited to yesterday's business problems. The legacy systems environment is terribly unintegrated. The legacy systems environment is built for the clerical community, and so forth.

ODS/Data Warehouse

One of the primary motivations of the ODS (operational data store) and the data warehouse environment is to come to grips with the inadequacies of the legacy systems environment. The ODS and the data warehouse provide a place where types of processing that cannot be accomplished in the legacy systems environment can occur. The net effect of the ODS and the data warehouse on the legacy systems environment is to "drain the swamp." By building the ODS and the data warehouse, data and processing are removed from the legacy systems environment which, over time, shrinks and simplifies.

Exactly what kind of data is removed by the building of the ODS and the data warehouse? There are several types of data that are removed:

Old, Archival Data

The legacy systems environment often contains a large amount of old data simply because there was no other place to put it. The old archival data is not needed for any kind of active processing but is found in the legacy systems environment because someone once placed it there and never thought to remove it. The data warehouse is an ideal place for storing old, inactive, once useful archival data.

Summary Information

The legacy applications environment is built primarily for the clerical community. As such the legacy applications environment contains almost exclusively detailed data. When summary data was occasionally created in the legacy environment, it was left in the legacy applications environment. Building the data warehouse environment provides a rational and organized place to store summary data.

Departmental Information

The legacy application environment is built one application at a time. The applications represent a narrow functional focus. When a departmental perspective is placed over the applications, a residue of data remains in the legacy environment. When the data warehouse is built, placing one or more data marts on top of the data warehouse is a convenient way to handle the needs of departmental data.

Unintegrated Applications

Building both the ODS and the data warehouse requires a high degree of integration of data. By building those architectural constructs, some unintegrated legacy applications simply disappear.

There are then many reasons why the ODS and the data warehouse environments have a very powerful "vacuum cleaner" effect on the legacy applications environment.

An interesting question: After the ODS and the data warehouse have been built, will there be any of the legacy applications environment remaining? Or will the advent of the ODS and the data warehouse environment completely remove the need for the legacy environment? What's left standing of the legacy environment after the ODS and the data warehouse are built?

The Remains

The remains of the legacy environment after the ODS and the data warehouse are built will be:

  • direct customer interaction and transaction,
  • collection of detailed information emanating from the customer transaction of business,
  • edits of transaction information collected, and
  • point-of-contact audit.

The legacy environment will have been transformed into a clerical, direct customer interface environment. The legacy environment will be that software that directs and manages initial customer entry of information into a system. Typical of such interchanges are the point at which a bank customer withdraws money from a bank, the point at which a policy is sold to an insuree, the point at which reservations are made for an airplane, the point at which a loan is made at a bank, etc. The remaining legacy environment will be highly stylized, in order to meet the business needs of the customer.
In a way, the remaining legacy systems environment serves as the point in which raw data needed for the running of the business of the corporation enters the corporation. The data enters in a detailed fashion. The raw detailed data is unintegrated and very customized to meet the needs of the customer and the particular application in which the data is entered. The data that is entered is very point-in-time oriented, reflecting an immediate business transaction. If by some chance the applications that collect the business transaction data are integrated, then the customer interface will appear to be very uniform.

Without the remains of the legacy system, there is no place for the raw data that reflects the day-to-day business of the corporation to be entered into the integrated, architected environment.

The advent of the ODS/data warehouse signals an extremely positive change in environments for the world of legacy systems. The ODS/data warehouse environment succeeds where reengineering has failed.

One of the interesting aspects of the draining of the swamp is that of the gradual, steady nature of the affair. There is nothing sudden or even very dramatic about the creation of the DSS environment. The effect that the establishment of the ODS/data warehouse environment has on the legacy environment is as gentle as the falling of the morning dew. You simply don't notice that anything is happening, and yet you wake one morning to find the dew in the meadow. The same holds true for the legacy environment. There is raging turmoil in the legacy environment one moment. Then, later on, after the ODS/data warehouse environment has grown, much of the stress of the legacy environment has been relieved. But at no time has the relationship between the two environments been very direct or obvious.

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