15.00 - USI Sizing Equation - Teradata Database

Teradata Database Design

Teradata Database
User Guide

USI Sizing Equation

The following parameter definitions are used with this equation:




Index Value Size

Size of the column set on which the USI is defined.

This must include any trailing pad bytes added for alignment purposes.

All row lengths must be an even number of bytes (see “Byte Alignment” on page 770), so be sure to take this into account.

Block Overhead

Sum of the following factors.

  • Block headers and trailers
  • Row headers and trailers
  • USI rowID
  • Spare byte
  • Presence bit arrays
  • Base table rowID
  •       = 28 bytes for an nonpartitioned primary index table

          = 30 bytes for a PPI table

    Packed64 Format Sizing Equations

    Aligned Row Format Sizing Equations

    If fallback is defined for the base table, then double the calculated result.

    Teradata Database implicitly creates a unique secondary index on any column set specified as PRIMARY KEY or UNIQUE, so you must take these indexes into consideration for your capacity planning as well. PRIMARY KEY and UNIQUE constraints are generally implemented as single‑table join indexes for temporal tables (see ANSI Temporal Table Support and Temporal Table Support for details). You must also take any of these system‑defined join indexes into account when doing capacity planning.