Physical design

The conceptual model is supposed to be independent of any physical considerations. The logical model is supposed to take account only of the fact that we are using a relational database. The physical design process, however, fine-tunes the model to suit a particular database platform which might include:

• Selecting datatype definitions for each column
• Designing constraints on the data
• Designing user views (covered in week 8)
• Designing indexes to improve query times (covered in week 8)

In addition, the physical design process investigates such practical details as:

• How the database files should be spread across one or more disks
• How much storage space is required
• How the data is likely to grow over time
• Designing security mechanisms (covered in week 11)
• Platform-specific performance tuning

Many of these activities fall to the database administrator (DBA), and are discussed in week 9. Much of the detail, however, is beyond the scope of this module.