CDM Considerations - Teradata Unity

Teradata® Unity™ User Guide

Product
Teradata Unity
Release Number
16.20
Published
May 2019
Language
English (United States)
Last Update
2019-05-23
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dzf1517499323110.ditamap
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dita:id
B035-2520
lifecycle
previous
Product Category
Analytical Ecosystem
In Unity 16.10 and later using CDM, the following are supported:
  • Updatable cursors or results sets
  • Writing to tables with Identity columns
    To avoid conflict between values set on different systems, CDM requires that you redefine the IDENTITY columns so they have different ranges on different systems. Replicating IDENTITY columns significantly affects performance.
Unity CDM is not compatible with Teradata Secure Zones (Multitenancy), and does not support the following Teradata Database features. If a client application issues a non-deterministic request that uses any of the following features, the request fails and an error Failure 4514 - Write disallowed because it contains a non-deterministic clause appears.
Some of the following features are supported with Unity SQL multicast.

Some features are supported by CDM replication, such as columnar tables, but require upgrading to the latest version of Teradata Database (16.20.29.01 or later).

CDM processing is subject to limitations on size and duration of requests. Transactions that require more than 20000 requests to replicate are not currently suitable for CDM; see the Unity configuration parameter TransactionRequestLimit. Similarly, transactions that take more than one hour to execute should not use CDM. CDM storage may also use significant amounts of space in the recovery log, and is subject to any configured thresholds on recovery log usage by a session (configuration parameters RecoveryLogGrowthSessionKillRate and RecoveryLogGrowthSessionKillThreshold).

Unity does not support non-deterministic requests if the request:
  • Uses a Load utilities such as FastLoad, MLoad, TPTLoad or MLoadX
  • Uses a Volatile table or Global temporary table
  • Uses the SQL syntax: CREATE TABLE … AS …
  • Issues a QueryGrid / SQL-H / Foreign Server request
  • Involves Teradata Secure Zones (Multitenancy)
  • Uses Unicode pass through characters
Workloads requiring CDM may experience both fixed and variable latency.