About Migrating User Data Tables - Teradata Database

Teradata Database Node Software Migration Guide

Product
Teradata Database
Release Number
15.10
Published
November 2017
Language
English (United States)
Last Update
2018-04-25
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B035-5942
lifecycle
previous
Product Category
Software

The time required to restore user data is greater than the time required to archive the data for several reasons, including the following:

  • For all tables with fallback protection, two rows (primary and fallback) are written during the restoration process, compared to only the primary row being written during the archival process.
  • If the destination system is configured differently than the source system, or the hash function has changed, rows may initially be sent to the incorrect AMP and then need to be rehashed and redistributed to the correct AMP.
  • A change in row format between the source and destination systems requires rebuilding each row field by field during restoration. Although restoring a system from an aligned row format to a packed row format will require 5 to 7 percent less space on the destination system, the restoration process may take 2 or 3 times as long as the archival process.

To more accurately estimate the time required for the restoration process, any changes between the source and destination systems should be discussed with Teradata Customer Services staff as part of the Change Control process prior to initiating migration.