Release 10.1A: OpenEdge Getting Started:
Database Essentials

Data layout

Proper database design is essential because all data originates from a storage area. Now review the important facts:

A database is made up of storage areas.
Each storage area can contain one or more objects.
A database object is a table or an index.
There are other objects, such as sequences and schema. At this point, you have no control over the storage location of these objects.
Each storage area can contain one or more extents or volumes on disk.
The extents are the physical files stored at the operating system level.
Each extent is made up of blocks, and you can determine the block size for your database. The block sizes that you can choose from are: 1KB, 2KB, 4KB, and 8KB.
You can have only one block size per database, but each area can have differing numbers of records per block.

There are several items to consider when determining the layout of a database. The first is your mean record size. This is easy to learn if you have an existing OpenEdge database; when you run a database analysis, this information is included in the output. The other information you must consider answers the following questions, and is generally not as easy for the database administrator to obtain because it requires knowledge of how the application is used. Even the designers of an application might not know how the users are taking advantage of the design. The questions are:

Is the table generally accessed sequentially or randomly?
Is the table frequently used or is it historical and thus used infrequently?
Do the users access the table throughout the day or only for reporting?
Are the individual records growing once inserted or are they mostly static in size?

The answers to these questions will help determine the size and layout of a database and allow you to take best advantage of your disks.