15.00 - Depot Area Overhead - Teradata Database

Teradata Database Design

Teradata Database
User Guide

Depot Area Overhead

The Depot consists of two types of slots:

  • Large Depot slots
  • Small Depot slots
  • The Large Depot slots are used by aging routines to write multiple blocks to the Depot area with a single I/O.

    The Small Depot slots are used when individual blocks that require Depot protection are written to the Depot area by foreground tasks.

    The number of cylinders allocated to the Depot area is fixed at startup. Consult your Teradata support representative if you want to change this value.

    The number of Depot area cylinders allocated is per pdisk, so their total number depends on the number of pdisks in your system. Sets of pdisks belong to a subpool, and the system assigns individual AMPs to those subpools.

    Because it does not assign pdisks to AMPs, the system calculates the average number of pdisks per AMP in the entire subpool from the vconfig GDO when it allocates Depot cylinders, rounding up the calculated value if necessary. The result is then multiplied by the specified values to obtain the total number of depot cylinders for each AMP. Using this method, each AMP is assigned the same number of Depot cylinders.

    The concept is to disperse the Depot cylinders fairly evenly across the system. This prevents one pdisk from becoming overwhelmed by all the Depot writes for your system.