Methodology – Monitoring and Tuning the Operational System

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Step 8 Consider the Introduction of Controlled Redundancy

To determine whether introducing redundancy in a controlled manner by relaxing the normalization rules will improve the performance of the system.

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Step 8 Consider the Introduction of Controlled Redundancy

Result of normalization is a logical database design that is structurally consistent and has minimal redundancy.

However, sometimes a normalized database design does not provide maximum processing efficiency.

It may be necessary to accept the loss of some of the benefits of a fully normalized design in favor of performance.

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Step 8 Consider the Introduction of Controlled Redundancy

Also consider that denormalization:– makes implementation more complex;– often sacrifices flexibility;– may speed up retrievals but it slows down

updates.

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Step 8 Consider the Introduction of Controlled Redundancy

Denormalization refers to a refinement to relational schema such that the degree of normalization for a modified relation is less than the degree of at least one of the original relations.

Also use term more loosely to refer to situations where two relations are combined into one new relation, which is still normalized but contains more nulls than original relations.

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Step 8 Consider the Introduction of Controlled Redundancy

Consider denormalization in following situations, specifically to speed up frequent or critical transactions:– Step 8.1 Combining 1:1 relationships– Step 8.2 Duplicating nonkey attributes in 1:*

relationships to reduce joins– Step 8.3 Duplicating foreign key attributes

in 1:* relationships to reduce joins

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Step 8 Consider the Introduction of Controlled Redundancy

– Step 8.5 Introducing repeating groups– Step 8.6 Merging lookup tables with base

relations– Step 8.7 Creating extract tables.

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Step 8.7 Creating Extract Tables

Reports can access derived data and perform multi-relation joins on same set of base relations. However, data the report is based on may be relatively static or may not have to be current.

Possible to create a single, highly denormalized extract table based on the relations required by the reports, and allow the users to access extract table directly instead of the base relations.

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Step 9 Monitor and Tune the Operational System

To monitor operational system and improve performance of system to correct inappropriate design decisions or reflect changing requirements.