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Lesson 8Extents in the data dictionary
ObjectiveStorage parameters from Oracle data dictionary.

Oracle Data Dictionary Storage Parameters

As with all the other attributes of database objects discussed in this course, you can explore the settings for storage parameters through views in the data dictionary.

Database objects

The USER_TABLES, USER_INDEXES, and USER_TABLESPACES views have columns that store the values for the storage parameters you can assign to these objects.
These columns hold the current values for these parameters.

Other views

There are other data dictionary views that provide information about how your Oracle database is using its storage space:

USER_EXTENTS: This view gives information about specific extents within a tablespace, including the relative position of an extent within the tablespace. A tablespace can contain many different database objects, and each object has its own extents, so the extents for any database object within a tablespace are usually mixed in with the extents for other database objects.
USER_SEGMENTS: The USER_SEGMENTS view has information about the segments belonging to a user, including the standard settings for INITIAL_EXTENT, MAX_EXTENTS, MIN_EXTENTS, and PCT_INCREASE. This view also contains a column called NEXT, but this column contains the value of the next extent that will be allocated, not the original value of the NEXT parameter.

Using Storage Manager

You can use the Storage Manager component of the Oracle Enterprise Manager, as shown in the following simulation, to check the available space in a tablespace as well as some of the dependencies on the tablespace.
Data Dictionary Extents
The next lesson demonstrates how Oracle uses free space within data blocks.