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`	File identifier number of the 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`