You executed the following command to create a tablespace called SALES_DATA: SQL>
CREATE TABLESPACE sales_data DATAFILE SIZE 100M SEGMENT SPACE
MANAGEMENT AUTO; Which two statements are true about the SALES_DATA
tablespace? (Choose two.)
A.
The database automatically determines the extent-sizing policy for thetablespace.
B.
The segments are automatically shrunk when the contents are removed from them.
C.
The allocation of extents within thetablespace is managed through the dictionary tables.
D.
The space utilization description of the data blocks in segments is recorded in bitmap
blocks.
E.
The space utilization description of the data blocks in segments is managed through free
lists.
When creating a locally managed tablespace, you can specify the extent allocation method to be used.
AUTOALLOCATE – means that the extent sizes are managed by Oracle.
Oracle will choose the optimal next size for the extents starting with 64KB. As the segments grow and more extents are needed, Oracle will start allocating larger and larger sizes ranging from 1Mb to eventually 64Mb extents. This might help conserve space but will lead to fragmentation. This is usually recommended for small tables or in low managed systems.
UNIFORM – specifies that the extent allocation in the tablespace is in a fixed uniform size. The extent size can be specified in M or K. The default size for UNIFORM extent allocation is 1M. Using uniform extents usually minimizes fragmentation and leads to better overall performance.
This section describes aspects of managing space in data blocks. Data blocks are the finest level of granularity of the structure in which database data is stored on disk. The size of a data block is specified (or defaulted) at database creation.
The PCTFREE and PCTUSED parameters are physical attributes that can be specified when a schema object is created or altered. These parameters allow you to control the use of the free space within a data block. This free space is available for inserts and updates of rows of data.