Space requirements for database objects

Estimating the size of database objects is an imprecise undertaking. Overhead caused by disk fragmentation, free space, and the use of variable length columns makes size estimation difficult, because there is such a wide range of possibilities for column types and row lengths.

After initially estimating your database size, create a test database and populate it with representative data. Then use the db2look utility to generate data definition statements for the database.

When estimating the size of a database, the contribution of the following must be considered:

• System catalog tables
• User table data
• Long field (LF) data
• Large object (LOB) data
• XML data
• Index space
• Log file space
• Temporary work space

Also consider the overhead and space requirements for the following:

• The local database directory file
• The system database directory file
• The file management overhead required by the operating system, including:
  • File block size
  • Directory control space