From VSAM to MongoDB

From VSAM to MongoDB

An organization facing big data pressures is migrating from VSAM to MongoDB. Although VSAM is 1970s technology, it stores data hierarchically which is very similar in structure to NoSQL document-based databases such as MongoDB. Therefore the data migration from VSAM to MongoDB could be straightforward. However, there is a debate going on whether a fully normalized relational logical data model should be built prior to migrating to MongoDB. Normalizing leads to well-understood structures and enables integration with existing data models. Some feel though that the effort to normalize will not be worth the value, because the current lack of metadata in the VSAM structures will lead to many unanswered questions that will only get answered once users can access the data in MongoDB. Also, there is a current lack of tools available for maintaining the lineage between the relational logical and the NoSQL physical, so the logical data model built may quickly become out of sync with its physical. What are your thoughts?


  1. Guido Bakema 5 years ago

    Never forget that things might be partially done in parallel. But keep also in mind that all organizations should always strive for building and maintaining an overall conceptual model.

  2. Bruce W 5 years ago

    I try to avoid using the word “relational” when talking to Big Data folks about data modeling. They hear the word relational and they think a relational data model must only apply to creating a relational DBMS. Instead I always describe it as a ERD (Entity Relationship Diagram) logical model and talk about the importance of understanding the business data (entities) and the business rules (relationships) imbedded in the flat file data.

  3. Janis LJ 5 years ago

    Systems that exist, especially older ones, should definitely go through a (re-)modeling phase. Often the structures that exist have plenty of flaws and misaligned attributes. Often it said that when making database, machine or software changes that the plan is to use the existing model to minimize costs and changes. This approach usually backfires and in past made me wonder why new system-project when all the flaws of the old one is carried forward. If you do not have time to review and improve at this point, you will never have the time.

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