CODASYL IDMS Data Warehouse Redundancy   Oracle Tips by Burleson Consulting

High Performance Data Warehousing

The CODASYL Generation Of Database Management  

Structural changes are a nightmare with network databases. Because the data relationships are hard linked with embedded pointers, the addition of an index or a new relationship requires special utility programs to "sweep" each and every affected record in the database. As each record is located, the prefix is restructured to accommodate the new pointers. Object-oriented databases encounter this same problem when a class hierarchy requires modification.

CODASYL databases were still far superior to any other technology of the day, and thousands of corporations began to implement their mission-critical systems on IDMS platforms. Even the Air Force used the IDMS database at the North American Air Defense Command (NORAD) to track incoming Soviet missiles (and, of course, Santa Claus at Christmas time). However, as soon as relational databases became fast and stable enough to support mission-critical systems, the cumbersome and inflexible CODASYL systems were abandoned.

Today, we see that the new object-oriented databases are remarkably similar to the CODASYL model. However, a data warehouse relies on the introduction of data redundancy to achieve its speed, and the pointer-based architecture of the network databases makes them less flexible than relational databases for warehouses.

Overall, we see that the CODASYL model is a database architecture that has been optimized for online record retrieval, and it’s not designed for data warehouse applications. While CODASYL records can be denormalized, the record location modes of CALC and VIA, do not allow for contiguous storage of records. Consequently, we see that data warehouse applications are not very well suited to this database architecture.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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