16.20 - Picking Sessions and Instances Automatically in Teradata PT Easy Loader - Parallel Transporter

Teradata® Parallel Transporter User Guide

Product
Parallel Transporter
Release Number
16.20
Published
August 2020
Language
English (United States)
Last Update
2020-08-27
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In Teradata PT Easy Loader, if the user does not provide a value for the number of sessions to use (through the MaxSessions attribute for the exporting or loading operator, then the values are defaulted to 32. For the number instances, the default is also 1.

This impacts performance since TPT job with 1 source session, target session and/or data stream to move large tables could be very slow.

In order to improve the usability of the product, we will try to determine, dynamically, the number of source/target sessions and operator instances depending on multiple factors including number of AMPs on source/target systems, size of data being moved, etc., to provide ideal performance for the objects being moved. In order to allow Easy Loader to dynamically determine the number of source/target sessions and operator instances, the user should not specify the value for <source_sessions>, <target_sessions> and/or <instances>.

If the user provides a value for the <source_sessions>, <target_sessions> or <instances> then the value provided by the user will be used for the job.

TPT will use the following formula to determine the sessions:
-----------------------------------------------------------------------------------------
              Data Size Small    Data Size Medium (Base)     Data Size Large  Data Size VLarge
                             
TPT LOAD/    Base * 0.5        If NumAmps <=20             Base             MIN(Base * 1.5,
    UPDATE/  (where Base is      then NumAmps                                    NumAmps)
    STREAM    calculation for    else MIN((20+NumAmps/20),
              MEDIUM)                 100)
-----------------------------------------------------------------------------------------
TPT will use the following formula to determine the instance count when the session count is not provided by the user:
-------------------------------------------------------------------------------------
     Data Size Small   Data Size Medium   Data Size Large   Data Size VLarge

TPT         1                 2                 4                  8
-------------------------------------------------------------------------------------

For a TPT job, the number if sessions and instances are calculated for each object being moved. So every object being moved could use a different combination of the source/target sessions and operator instances to provide optimal performance to copy that particular object.

For TPT, the sessions computed are the total sessions that will be used to move a particular object. For example, when moving a large object with TPT_LOAD, if the LOAD sessions were computed as 12 and operator instances were computed as 2, then each instance will use 12/2 = 6 sessions to move that particular large object.

The status output displays the number of sessions and instances used to move each object. There are several factors such as Network Capacity, available CPU etc. that affect performance of a job. The user can choose to specify the values for source/target sessions and data streams if the specified values better suit their requirements.

If TASM Utility session rules is enabled on a particular source or target system, then TASM may override the TPT operator sessions.