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Dba_segments describes the storage space allocated for all segments in the database.

User_segments describes the storage allocated for segments owned by the current user's object. This view does not display owner, HEADER_FILE, HEADER_BLOCK, or RELATIVE_FNO columns.

Column

Datatype

NULL

Description

OWNER

VARCHAR2 (30)

Username of the segment owner

The owner of the segment

SEGMENT_NAME

VARCHAR2 (81)

Name, if any, of the segment

The name of the segment

PARTITION_NAME

VARCHAR2 (30)

Object Partition Name (Set to NULL for non-partitioned objects)

Name of the corresponding segment of the partition table

SEGMENT_TYPE

VARCHAR2 (18)

Type of segment:

* NESTED TABLE

* TABLE

* TABLE PARTITION

* CLUSTER

* LOBINDEX

* INDEX

* INDEX PARTITION

* LOBSEGMENT

* TABLE SUBPARTITION

* INDEX SUBPARTITION

* LOB PARTITION

* LOB SUBPARTITION

* ROLLBACK

* TYPE2 UNDO

* DEFERRED ROLLBACK

* TEMPORARY

* CACHE

* SPACE HEADER

* UNDEFINED

Type of segment

SEGMENT_SUBTYPE

VARCHAR2 (10)

Subtype of LOB segment: SECUREFILE, ASSM, MSSM, and NULL

Subtypes of LOB segments: SECUREFILE, ASSM, MSSM, and NULL

TABLESPACE_NAME

VARCHAR2 (30)

Name of the tablespace containing the segment

The name of the table space containing the segment

HEADER_FILE

NUMBER

ID of the file containing the segment header

Indicates which data file the header of this segment is in, because the segment can span data files.

HEADER_BLOCK

NUMBER

ID of the block containing the segment header

Indicates that the header of this segment is in the block of the data file

BYTES

NUMBER

Size, in bytes, of the segment

The size of the segment. Default: bytes

BLOCKS

NUMBER

Size, in Oracle blocks, of the segment

How many blocks are occupied by the segment?

EXTENTS

NUMBER

Number of extents allocated to the segment

How many extent have been allocated

INITIAL_EXTENT

NUMBER

Size in bytes requested for the initial extent of the segment at create time. (Oracle rounds the extent size to multiples of 5 blocks if the requested size is greater than 5 blocks.)

The size in bytes requested for the initial segment of the segment at the time of creation. (if the requested size is greater than 5 blocks, Oracle rounds the segment size to a multiple of 5 blocks.)

NEXT_EXTENT

NUMBER

Size in bytes of the next extent to be allocated to the segment

The next assigned extent size in byte. If it is empty, it is automatically assigned.

MIN_EXTENTS

NUMBER

Minimum number of extents allowed in the segment

Minimum number of extent allocated (in number)

MAX_EXTENTS

NUMBER

Maximum number of extents allowed in the segment

Maximum number of extent allocated (in number)

MAX_SIZE

NUMBER

Maximum number of blocks allowed in the segment

The maximum number of blocks sizes allocated

RETENTION

VARCHAR2 (7)

Retention option for SECUREFILE segment

Retention options for security segments

MINRETENTION

NUMBER

Minimum retention duration for SECUREFILE segment

Minimum hold time for securefile segment

PCT_INCREASE

NUMBER

Percent by which to increase the size of the next extent to be allocated

Percentage increase in the next extent allocation

FREELISTS

NUMBER

Number of process freelists allocated to this segment

Specifies a list of all data blocks available for insert operations to manage free space below HWM

FREELIST_GROUPS

NUMBER

Number of freelist groups allocated to this segment

The number of free list groups assigned to this segment

RELATIVE_FNO

NUMBER

Relative file number of the segment header

The relative file number of the paragraph header

BUFFER_POOL

VARCHAR2 (7)

Buffer pool to be used for segment blocks:

DEFAULT

KEEP

RECYCLE

Blocks used in the middle of Buffer pool

FLASH_CACHE

VARCHAR2 (7)

Database Smart Flash Cache hint to be used for segment blocks:

DEFAULT

KEEP

NONE

Solaris and Oracle Linux functionality only.

Database Smart Flash Cache prompt segment blocks mode

CELL_FLASH_CACHE

VARCHAR2 (7)

Cell flash cache hint to be used for segment blocks:

DEFAULT

KEEP

NONE

See Also: Oracle Exadata Storage Server Software documentation for more information

The Cell flash cache prompt is used for table blocks

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