7.83 DBA_UNDO_EXTENTS

DBA_UNDO_EXTENTS describes the extents comprising the segments in all undo tablespaces in the database.

Note:

The status of the undo space distribution reported by DBA_UNDO_EXTENTS is correct for the undo tablespace that is active on the instance on which DBA_UNDO_EXTENTS is queried. However, due to the use of in-memory information that is different on each instance, there can be a discrepancy in the status of the undo space distribution of undo tablespaces active on other instances when queried from one instance. This does not affect undo functionality and is only a reporting discrepancy for other instances' undo tablespace space distribution status. As a best practice, query the space distribution for an undo tablespace from the instance on which it is active.

Column Datatype NULL Description

OWNER

CHAR(3)

Owner of the undo tablespace

SEGMENT_NAME

VARCHAR2(128)

NOT NULL

Name of the undo segment

TABLESPACE_NAME

VARCHAR2(128)

NOT NULL

Name of the undo tablespace

EXTENT_ID

NUMBER

ID of the extent

FILE_ID

NUMBER

NOT NULL

Absolute file number of the data file containing the extent

BLOCK_ID

NUMBER

Start block number of the extent

BYTES

NUMBER

Size of the extent (in bytes)

BLOCKS

NUMBER

Size of the extent (in blocks)

RELATIVE_FNO

NUMBER

Relative number of the file containing the segment header

COMMIT_JTIME

NUMBER

Commit time of the undo in the extent expressed as Julian time. This column is deprecated, but retained for backward compatibility reasons.

COMMIT_WTIME

VARCHAR2(20)

Commit time of the undo in the extent expressed as Wallclock time.This column is deprecated, but retained for backward compatibility reasons.

STATUS

VARCHAR2(9)

Transaction Status of the undo in the extent:

  • ACTIVE

  • EXPIRED

  • UNEXPIRED