15.00 - MaxLoadAWT - 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

MaxLoadAWT

Purpose  

Specifies the combined number of AMP Worker Tasks (AWTs) that can be used by FastLoad and MultiLoad at any time. It allows more FastLoad, MultiLoad, and FastExport tasks (jobs) to run concurrently, and sets a limit on AWT usage to prevent excessive consumption or exhaustion of AWT resources.

This field also acts as a “switch” on the function of MaxLoadTasks field:

  • When MaxLoadAWT set to zero, the number of load utilities that can run concurrently is controlled entirely by the MaxLoadTasks field. In this case, MaxLoadTasks specifies the maximum number of combined FastLoad, MutiLoad, and FastExport jobs that can run concurrently.
  • When MaxLoadAWT is set to an integer greater than zero, MaxLoadTasks applies only to the combined number of FastLoad and MultiLoad jobs, which are also limited by the MaxLoadAWT setting. In this case, the number of FastExport jobs that can run is always 60 minus the number of combined FastLoad and MultiLoad jobs currently running.
  • Note: Throttle rules for load utility concurrency set in the Teradata Viewpoint Workload Designer portlet override the MaxLoadAWT setting, unless MaxLoadAWT is set to the maximum.

    Field Group

    General

    Valid Settings

    If MaxLoadAWT is set to a non-zero value, it should be a value greater than or equal to five, which allows at least one FastLoad and one MultiLoad job to run concurrently.

    The maximum allowable value is 60% of the total AWTs per AMP. By default, the maximum number of AWTs started for each AMP vproc is 80, so the default maximum value for MaxLoadAWT is 48.

    Default

    0

    Changes Take Effect

    After the DBS Control Record has been written. A system restart is not required.

    Usage Notes  

    Consider using MultiLoad, rather than FastLoad, especially in cases of many small load jobs. MultiLoad generally consumes fewer AWTs per job than FastLoad.

    The MaxLoadAWT field works together with the MaxLoadTasks field to limit the number of concurrent load utilities allowed to run:

  • If MaxLoadAWT is zero (the default):
  • MaxLoadTasks can be an integer from zero through 15.
  • The MaxLoadTasks field specifies the maximum number of combined FastLoad, MultiLoad, and FastExport jobs that can run concurrently.
  • The system does not consider the number of available AWTs when limiting the number of load utilities that can run concurrently.
  • If MaxLoadAWT is greater than zero:
  • MaxLoadTasks can an integer from zero through 30.
  • The MaxLoadTasks field sets the maximum number of combined FastLoad and MultiLoad jobs that can run concurrently. MaxLoadTasks does not directly limit the number of FastExport jobs that can run.
  • The number of combined FastLoad and MultiLoad jobs that can run concurrently is limited by the values of both the MaxLoadTasks field and the MaxLoadAWT field. When either limit is met, no further FastLoad or MultiLoad jobs are allowed to start until the limiting factor is reduced. See “About AWTs” on page 369.
  • The maximum number of load utility jobs of any type—FastLoad, MultiLoad, or FastExport—that can run concurrently is 60. Consequently, the number of FastExport jobs allowed to run at any time is 60 minus the number of combined FastLoad and MultiLoad jobs that are running.
  • For example, if the sum of currently running FastLoad and MultiLoad jobs is 29, the number of FastExport jobs that can be started is 31 (60 minus 29), regardless of the MaxLoadAWT and MaxLoadTasks settings.

  • If MaxLoadAWT is set to anything greater than zero, it can only be reset to zero if MaxLoadTasks is 15 or less.
  • Because load utilities share system resources with other system work, such as tactical and DSS queries, limiting the number of load utility jobs can help ensure sufficient system resources are available for other work.

    About AWTs

    AWTs are processes dedicated to servicing the Teradata Database work requests. A fixed number of AWTs are pre-allocated during Teradata Database system initialization for each AMP vproc. Each AWT looks for a work request to arrive in the Teradata Database system, services the request, and then looks for another. An AWT can process requests of any work type.

    The number of AWTs required by FastLoad and MultiLoad changes as their jobs run. More AWTs are required in the early phases of the jobs than in the later phases. Teradata Database dynamically calculates the total AWTs required by active jobs, and allows more jobs to start as AWTs become available. If MaxLoadAWT is greater than zero, new FastLoad and MultiLoad jobs are rejected when the MaxLoadAWT limit is reached, regardless of the MaxLoadTasks setting. Therefore, FastLoad and MultiLoad jobs may be rejected before MaxLoadTasks limit is reached.

    Example  

    FastLoad and MultiLoad require different numbers of AWTs at different phases of execution. The following table shows how many AWTs are used at each phase.

     

    Load Utility and Phase

    Number of AWTs Required

    FastLoad: Loading

    3

    FastLoad: End Loading

    1

    MultiLoad: Acquisition

    2

    MultiLoad: Application

    1 per target table

    Assume that MaxLoadAWT = 48 and MaxLoadTasks = 30. The list below shows some permitted combinations of load utility jobs. The limiting condition(s) for each combination is shown in bold:

  • 16 FastLoads in Loading phase
         16 concurrent load tasks
         
    48 AWTs in use: (16 x 3)
  • 9 FastLoads in Loading phase and 21 FastLoads in End Loading phase
         
    30 concurrent load tasks
         48 AWTs in use: (9 x 3) + (21 x 1)
  • 24 MultiLoads in Acquisition phase
         24 concurrent load tasks
         48 AWTs in use: 24 x 2
  • 5 MultiLoads in Acquisition phase and 25 MultiLoads in Application phase
         30 concurrent load tasks
         35 AWTs in use: (5 X 2) + (25 x 1)
  • 6 FastLoads in Loading phase and 15 MultiLoads in Acquisition phase
         21 concurrent load tasks
         48 AWTs in use: (6 x 3) + (15 x 2)