Size Category 

Use

You use the size category to define the expected space required for the table in the database. You can choose a size category from 0 to 4 for your table. A certain fixed memory size in the database, which depends on the database system used, is assigned to each category.

Features

When you create a table, the system reserves initial space (an initial extent) in the database. If more space is required at a later time due to data entries, additional memory is added depending on the selected size category. This is explained in the following figure.

Selecting the correct size category prevents the creation of a large number of small extents for a table. It also prevents the waste of space if extents that are too large are created.