15.00 - Random AMP Samples - System Emulation Tool

Teradata System Emulation Tool User Guide

prodname
System Emulation Tool
vrm_release
15.00
category
User Guide
featnum
B035-2492-034K

Random AMP Samples

Select the Random AMP Samples check box to export the data distribution of a table on one or more randomly selected AMPs based on the type of export operation.

When exporting by query, this option exports the RAS for the tables referenced by the specified queries.

When exporting by database, this option exports the RAS of the tables selected for export.

When exporting by workload, this option exports the RAS for the tables referenced by the workload queries.

TLE must be turned on before setting RAS. Be aware that TLE might cause system performance degradation. For more information on TLE, refer to SQL Request and Transaction Processing B035-1142.

To change the RAS export options

1 From an export dialog box, click Options.

The Export Options dialog box appears.

2 [Optional] In the RAS tag box, type a new file name.

By default, the RAS tag box displays the file name entered when choosing an export method in the Export from Teradata Database dialog box.

Note: No more than 128 tables can be selected in the current session. However, an unlimited number of rows can be exported from SystemFE.Opt_RAS_Table.

3 Click Select Tables.

The Export Random AMP Samples (RAS) dialog box appears.

Figure 8: Export Random AMP Samples (RAS)

4 Under Select Table Names, do one of the following:

  • Select the tables to export.
  • Click Select All.
  • 5 To define the way that RAS are exported, select an option.

     

    Option

    Description

    Capture from Source

    Export RAS from SystemFE.Opt_RAS_Table and allow the use of RAS already added to SystemFE.Opt_RAS_Table. These samples can be added manually to SystemFE.Opt_RAS_Table using another tool, such as using the DIAGNOSTIC DUMP statement in Basic Teradata Query (BTEQ).

    Capture from AMPs

    Export samples from the target system. Use this option to export samples for the selected row directly from the AMPs. This option exports samples to SystemFE.Opt_RAS_Table using the RAS tag specified in the RAS tag box. The samples are deleted after the row is exported.

    Note: If the row exists in SystemFE.Opt_RAS_Table, the Duplicate Random AMP Samples (RAS) dialog opens, enabling the user to select the required option. See Figure 9 on page 91.

    Set Samples

    Set the RAS for the selected row before exporting. This ensures that the Optimizer uses this set of samples when generating an execution plan. Only one RAS can be set for each table selected.

    Note: This option is available only when exporting by query.

    6 Click OK to close the Export Random AMP Samples (RAS) dialog box and return to the Export Options dialog box.

    7 Click OK to close the Export Options dialog box.

    Export Options for RAS Duplicate Keys

    The following screen image is referenced in the table above in the Capture from AMPs option. The export options are described below this image.

    Figure 9: Duplicate Random AMP Sample

    Note that the option chosen is utilized for the remaining Duplicate Random AMP Sample.

     

    Option

    Description

    Delete and Recollect Sample.

    Deletes the existing stale Random AMP Sample (RAS), and exports RAS to SystemFE.Opt_RAS_Table. The row is deleted after export operation.

    Export existing Sample from Opt_RAS_Table.

    Exports the existing sample.

    Ignore. Do not export this sample.

    Skips the export of RAS for this tag.

    Do not show this dialog again.

    When checked, the Duplicate Random AMP Sample dialog box is not invoked for the remaining Duplicate RAS errors and the RAS export option chosen previously is used to resolve Duplicate RAS errors observed during the remaining export operation.