Estimating table size

You can calculate the approximate sizes (in disk pages) of tables.

For a description of size calculations for indexes, see Estimating index pages.

The disk pages allocated to a table are collectively referred to as a tblspace. The tblspace includes data pages. A separate tblspace includes index pages. If simple large objects (TEXT or BYTE data) are associated with a table that is not stored in an alternative dbspace, pages that hold simple large objects are also included in the tblspace.

The tblspace does not correspond to any fixed region within a dbspace. The data extents and indexes that make up a table can be scattered throughout the dbspace.

The size of a table includes all the pages within the tblspace: data pages and pages that store simple large objects. Blobpages that are stored in a separate blobspace are not included in the tblspace and are not counted as part of the table size.

The following sections describe how to estimate the page count for each type of page within the tblspace.

Tip: If an appropriate sample table exists, or if you can build a sample table of realistic size with simulated data, you do not need to make estimates. You can run oncheck -pt to obtain exact numbers.

Copyright© 2020 HCL Technologies Limited