15.00 - Performance Groups - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
15.00
Content Type
Configuration
Publication ID
B035-1102-015K
Language
English (United States)
Last Update
2018-09-25

Performance Groups

Every request is assigned to a Performance Group (PG) based on the session logon process and by Teradata Active System Management (TASM), if enabled. PGs determine the priorities of Teradata Database jobs (mostly database queries) that are run from the session. Each PG is associated with a Resource Partition and one or more Allocation Groups. It is the interaction of Resource Partition and Allocation Group weights that determines the priority of jobs that are run from a particular Teradata Database session.

Allocation Groups are dynamically assigned to Performance Groups according to relationships defined by Performance Periods. The specific Allocation Group associated with a Performance Group can change based on the time of day or the resource usage of running jobs. Performance Periods define which Allocation Group is assigned to a Performance Group at any moment based on these conditions.

For more information on Performance Periods, see “Performance Periods” on page 710. For more information on Allocation Groups, see “Allocation Groups” on page 715.

The Resource Partition and Performance Periods of a Performance Group are specified when the PG is created using the schmon -p command. The following table briefly describes the parameters used to define a Performance Group. For more information on the schmon -p command, see“schmon -p” on page 762.

 

Parameter

Description

Performance Group ID

An integer from 0 through 249.

Note: Priority Scheduler provides four predefined Performance Groups, having IDs 0 through 3. These Performance Groups are associated with Resource Partition 0.

Performance Group Name

The name of the Performance Group that allows it to be assigned to a session. For more information, see “Performance Group Names” on page 708.

Resource Partition ID

An integer from 0 through 4 that identifies the Resource Partition owning the Performance Group. For more information, see “Resource Partitions” on page 705.

Performance Period Type

A code that indicates the type of milestone limits used to define Performance Periods. All Performance Periods of a Performance Group will be the same type. For more information, see “Performance Period Types and Limits” on page 711.

Performance Periods

Specifications for one to eight Performance Periods. Each period is defined by a milestone limit and an Allocation Group identifier.

You can express milestone limits in the following units:

  • Time-of-day
  • Session resource usage
  • Query resource usage
  • Performance Group Names

    Performance Group names must be unique and not longer than 16 characters. Use names that represent the type of work performed in each group, or that relate the groups to their associated Resource Partitions.

    Priority Scheduler provides four predefined Performance Groups, L, M, H, and R, within default Resource Partition 0. These groups correspond to low, medium, high, and rush, and determine the priorities given to jobs started under the control of sessions associated with these PGs.

    The following table lists the predefined Performance Groups for default Resource Partition 0. The weights listed are those of the Allocation Group associated with each Performance Group. Each predefined Performance Group doubles the weight assigned to the previous lower-valued Performance Group. These weights are used when assigning priorities to jobs running under each Performance Group. For more information on Allocation Groups, see “Allocation Groups” on page 715.

     

    Default Performance Group

    Default Weight

    L

    5

    M

    10

    H

    20

    R

    40

    Assigning Performance Groups to Users

    When a user logs on to the system, the session is assigned to a Performance Group that determines the priority of session jobs. Generally, each user has access to a limited subset of Performance Groups. This subset is listed in the user’s account ID string, which is specified as part of the CREATE USER and MODIFY USER statements. The entire account ID string is limited to 30 characters, and stored in the Teradata DatabaseData Dictionary.

    The following rules apply to formatting Performance Group names in account ID strings:

  • Use apostrophes to delimit each PG name.
  • Immediately preface each name with a dollar sign ($).
  • Names longer than a single character require terminating dollar signs. Single-character names do not require the terminal $, but may include it.
  • Because the entire account ID string is limited to 30 characters, try to keep PG names brief.
  • Note: The Teradata Database enforces other rules for the length and format of account ID strings, which may influence the choice of Performance Group names. For more information on CREATE USER, MODIFY USER, and the Data Dictionary, see the books SQL Data Definition Language and Data Dictionary.

    The following are examples of valid Performance Group names that might appear in an account ID string for a user granted access to five Performance Groups:

    ‘$L’,'$L1$',’$M$’,$M2$',’$tac1$’

    Assigning Performance Groups to Logon Sessions

    Every logon session is assigned to a Performance Group, which determines the priority of jobs started during that session. Users can specify one of their assigned Performance Groups when they log on to Teradata Database. If no Performance Groups are specified during logon, the session defaults to the pre-defined Performance Group M in Resource Partition 0.

    The following example shows a user logging on to Teradata Database and specifying the M2 Performance Group:

    .logon testdb/itbatch, cab,'$M2$'

    The following table describes how Teradata Database assigns Performance Groups to sessions during the logon process.

     

    IF...

    THEN...

    the logon command includes a Performance Group name matching one of the PGs assigned to the user

    the session is assigned to the specified PG.

    the logon command does not include a Performance Group name

    the session is assigned to the first Performance Group specified in the user’s account ID string. If no PG is specified in the account ID string, the session defaults to Performance Group M.

    the logon command includes a Performance Group name that is not specified in the account ID string portion of the user record)

    logon fails.

    the logon command includes a Performance Group that is specified in the user’s account ID string, but that has not yet been created using the schmon -p command

    the session defaults to Performance Group M.