Basis

Logical Database Design

Physical Database Design

Task

Maps  or  transforms  the  conceptual schema (or an ER schema) from the high-stages data model into a relational database schema.

The specifications for the stored database within terms of physical storage structures, record placement, and indexes are designed.

Choice of criteria

The mapping can proceed in two levels:

1. System independent mapping but data model-depending.

2. tailoring the schemas to a specific DBMS.

The following criteria are frequent used to guide the choice of physical database design option:

1. Response Time option

2. Space Utilization

3.Transaction throughout

Result

DDL statements within the language of the chosen DBMS that specify the conceptual and external stages schemas of the database system. But if the DDL statements involve a few physical design parameters, a completed DDL specification must wait until after the physical database.

An initial determination of storage structures and  the access  paths  for the database files. This corresponds to defining the internal schema in terms of Data Storage Definition Language.