Setting LOB preferences

You use the LOBs page of the Preferences dialog to specify options that will control retrieving and saving LOB data.

About this task

LOB data (Large Object data) is large text or binary objects in a database. LOBs can be large strings of text, images, and so on. If a query result set contains a large amount of LOB data, processing resources could be severely strained. The LOB preferences page contains a number of LOB data retrieval restrictions that you can use to manage repository resources. To specify LOB data preferences:

Procedure

  1. Select View > Preferences. The Preferences window opens. Select LOBs from the tree.
  2. Check Override LOB options if possible to grant yourself the ability to override the LOB options that have been specified by your QMF administrator for your resource limits group. Your administrator must have given your resource limits group permission to override the LOB options. If you do not have permission to override LOB options, this check box is not available.
  3. Use the LOB Retrieval Option radio buttons to specify how large object data (LOB) will be retrieved. There are four choices:
    • Select Disable LOB columns to disable LOB data retrieval. By selecting this option, you will not be able to query any table that contains LOB data.
    • Select Disable LOB data retrieval to disable LOB data retrieval but allow access to the other columns in the tables that contain LOB data. By selecting this option, you can query tables that contain LOB data and result data for all columns except those that contain LOBs will be returned.
    • Select Retrieve LOB data on demand to specify that you want to retrieve all LOB data from a table but only display selected columns of the LOB data in the query results.

      By selecting this option, you can query tables that contain LOB data and your result data will be returned for all columns that contain LOB objects. To conserve resources, however, the retrieved LOB data is stored in a file. Pointers (<LOB LOCATOR>) to the LOB data objects are displayed in the query results. You click the pointer to view the LOB data.

      You can also pull the data from the database by double-clicking on the pointer.

    • Select Retrieve LOB data automatically to specify that you want to retrieve all LOB data from a table and immediately display the retrieved LOB data in the query results.

      This option pulls ALL of the LOB data for ALL of the LOB columns from the database to the local computer. The actual LOB data is not displayed in grids and reports. Instead, pointers to the LOB data are displayed.

      This option can potentially consume a large amount of resources on the local computer.

  4. Use the LOB Saving Option radio buttons to specify whether you can save large object data (LOB). There are two choices:
    • Select Disable LOB data to disable saving LOB data on a database data source.
    • Select Enable LOB data to allow saving LOB data on a database data source.
  5. Specify the maximum size of a LOB column in the Maximum LOB column size field. You specify the size in kilobytes, up to 2G (the maximum LOB size). The default is 0, which specifies there is no maximum size. If you query a table with LOB data that is larger than the maximum, the LOB data will not be returned for display.
  6. Click Apply to save your preferences choices.
  7. Click Restore Defaults to restore the default preference values.
  8. Click Apply and Close to close the Preferences window.