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Without knowing specifics, here is my general recommendation for cases like this:
- Maintain history in a new, separate history database. When you add, change, or delete a record, write history. The history record should look like the regular record, but with at least a timestamp attached. Additional information may be desirable. The timestamp should be indexed.
- Keep a history QVD separate from the live QVD.
- Use an incremental load when building the history QVD. The timestamp index will allow you to do this efficiently.
Why I wouldn't do it in QlikView:
- A series of snapshots of a database is NOT a full history of that database. It might be sufficient for now, but may not be in the long run.
- A QlikView history is useless to you if a program in your source system needs history at some point. Don't build it twice. Build it once, in the source system.
- QlikView is a reporting system, not a data-processing system. History seems to me more of a data-processing requirement.
- QlikView can have accuracy issues, such as with the storage of fractions.