6.87 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