Specifying LOB Options resource limits

The LOB Options resource limits control a users ability to access, retrieve, and save data to and from tables containing large objects (LOBs).

A Large Object (LOB) is a Db2® for z/OS® and Db2 for Linux®, UNIX, and Windows data type that houses non-traditional data such as text, multimedia, image, video, photograph, sound, or any very large data file inside a database table. Retrieving or saving LOB data can consume a substantial amount of resources. Even just accessing a table that contains LOB data can be resource consumptive. Using the LOB Options resource limits, you can control access to tables on the database data source that include LOB data. LOB Options resource limits can be applied to both data sources and individual queries.

The LOB Options resource limits are as follows:

LOB Retrieval Option
This field specifies whether a user can retrieve large object (LOB) data when this schedule is in effect. You can select one of the following:
  • Disable LOB columns specifies that users can not retrieve LOB data and can not query or access any table that contains LOB data.
  • Disable LOB data retrieval specifies that users can not retrieve LOB data but can query tables that contain LOB data. Query result data will be returned for all columns in the table except those that contain LOB data.
  • Retrieve LOB data on demand specifies that users can query tables that contain LOB data and result data will be returned for all columns including those columns that contain LOB objects. However, the results data for the LOB columns will not actually be displayed in the column. A pointer is displayed. When the user selects the pointer, the LOB data will be displayed in the query results.

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

  • Retrieve LOB data automatically specifies that users can query tables that contain LOB data and the result data will be returned for all columns, including those columns that contain LOB objects.

    This option pulls ALL of the LOB data for ALL of the LOB columns from the database to the local computer.

    This option can potentially consume a large amount of resources and time. The actual LOB data is not displayed in grids and reports. Instead, pointers to the LOB data are displayed.

Enable saving LOB data
This field specifies whether users can save LOB data on the database data source.
Maximum LOB column size
This field specifies the maximum size of a LOB column, in kilobytes, up to 2G (the maximum LOB size). The default is 0, no maximum. If a user queries a table with LOB data that is larger than the maximum, the LOB data will not be returned for display.
LOB options can be overridden
This field specifies whether a user can override the default LOB Options resource limits that have been specified for their group.