SESSIONS - FastLoad

Teradata FastLoad Reference

Product
FastLoad
Release Number
15.10
Language
English (United States)
Last Update
2018-10-07
dita:id
B035-2411
lifecycle
previous
Product Category
Teradata Tools and Utilities

Purpose  

The SESSIONS command specifies how many Teradata FastLoad sessions will be logged on when a LOGON command is entered and, optionally, the minimum number of sessions required to run the job.

Syntax  

where

 

Syntax Element

Description

max

Maximum number of sessions to log on.

The max specification must be greater than zero.

The default, if the SESSIONS command is not used, is one session for each AMP.

min

Minimum number of sessions required for the job to continue.

The min specification must be greater than zero.

The default, if the SESSIONS command is not used, is 1.

*

Minimum and maximum number of sessions.

Using the asterisk character as the max specification logs on for the maximum number of sessions—one for each AMP.

Using the asterisk character as the min specification logs on for at least one session, but less than or equal to the max specification.

Note:  

1 )
Specifying SESSIONS * * has the same effect as not using the SESSIONS command at all.
2 )
On large to very large Teradata Database configurations, the default of one session per AMP may be inappropriate.

* (continued)

There is no general method to determine the optimal number of sessions, because it is dependent on several factors, including, but not limited to:

  • Teradata Database performance and workload
  • Client platform type, performance, and workload
  • Channel performance, for mainframeattached systems
  • Network topology and performance, for networkattached systems
  • Volume of data to be processed by the application
  • Using too few sessions is likely to unnecessarily limit throughput. On the other hand, using too many sessions can increase session management overhead (and also reduce the number of sessions available to any other applications) and may, in some circumstances, degrade throughput.

    Regardless of the size of the Teradata Database configuration, for large repetitive production applications, it will usually be appropriate to experiment with several different session configurations to determine the best tradeoff between resource utilization and throughput performance.

    For larger Teradata Database configurations, it is appropriate to establish an installation default for the maximum number of sessions that is less than one session per AMP. This can be done either via the installation configuration file (see “Teradata FastLoad Configuration File” on page 50) or via a standard runtime parameter (see “Mainframe‑Attached Runtime Parameters” on page 35). An installation default for number of sessions, if specified in the configuration file, can be overridden in individual Teradata FastLoad job scripts, when necessary.

    Usage Notes  

    Table 49 describes the things to consider when using the SESSIONS command.

     

    Table 49: Usage Notes for SESSIONS 

    Topic

    Usage Notes

    DBS Support TASM

    If the DBS supports TASM, the SESSIONS command has no effect since the number of sessions is determined by the DBS setup rules, Please refer to TRP 5410007249 for DBS support TASM document. If FastLoad must connect to the exact number of sessions required by the DBS, otherwise FastLoad will displays the following message and terminates the job:

    The number of FastLoad connections (n1) is not the same as the number of connections returned by CHECK WORKLOAD END (n2) where n1 is the number of sessions that FastLoad can connect and n2 is the number of sessions that FastLoad must connect to required by the DBS.

    Entering the SESSIONS Command

    The SESSIONS command must be entered before the LOGON command in the Teradata FastLoad job.

    Session Number Limits

    Regardless of the number of sessions specified, the actual number of sessions Teradata FastLoad uses is limited to the number of AMPs available on the Teradata Database. Thus, there is no guarantee that the number of sessions specified in the command will actually be logged on.

    Reported Number of Sessions

    Teradata FastLoad reports the number of sessions logged on when a LOGON command is executed.

    Invalid Number of Sessions

    The maximum relevant number of sessions which can be specified is 32767. Teradata FastLoad disregards any larger number and logs on for as many sessions as it can, one session per available AMP as indicated in the Teradata FastLoad error message:

    FDL4867 Invalid number of sessions requested
    FastLoad will log on as many sessions as possible

    Example  

    The following example specifies five Teradata FastLoad sessions:

    SESSIONS 5 ;

    Example  

    The following example specifies ten Teradata FastLoad sessions, with a minimum of five:

        SESSIONS 10 5 ;
    Completion Message

    The Teradata FastLoad completion message is:

        FDL4866 SESSIONS command accepted