Determining How an Entity Should Be Stored › Guidelines for Determining How an Entity Should Be Stored › Is This a Parent Entity but Not a Child Entity?

Is This a Parent Entity but Not a Child Entity?

Ask this question for each entity that does not exist as both a parent and a child.

An entity that exists only as a parent entity is often used as an entry point into the database. For this reason, it is advisable to have a fast access key on the entity.

The CALC location mode generally is a better choice than an index key because:

• It requires fewer I/Os to access an entity using a CALC key.
• The CALC algorithm randomizes entity occurrences, thus allowing space to cluster related entity occurrences.

Example

An example of a parent entity but not a child entity is the DEPARTMENT entity. This entity should be stored CALC based on the DEPT ID.