DBA_HIST_ROLLSTAT

DBA_HIST_ROLLSTAT displays historical rollback segment statistics. This view contains snapshots of V$ROLLSTAT.

Column	Datatype	NULL	Description
`SNAP_ID`	`NUMBER`	`NOT NULL`	Unique snapshot ID
`DBID`	`NUMBER`	`NOT NULL`	Database ID for the snapshot
`INSTANCE_NUMBER`	`NUMBER`	`NOT NULL`	Instance number for the snapshot
`USN`	`NUMBER`	`NOT NULL`	Rollback segment number
`EXTENTS`	`NUMBER`		Number of extents in the rollback segment
`RSSIZE`	`NUMBER`		Size (in bytes) of the rollback segment. This value differs from the value of the `BYTES` column of the `DBA_SEGMENTS` views by the number of bytes in one database block.
`WRITES`	`NUMBER`		Number of bytes written to the rollback segment
`XACTS`	`NUMBER`		Number of active transactions
`GETS`	`NUMBER`		Number of header gets
`WAITS`	`NUMBER`		Number of header waits
`OPTSIZE`	`NUMBER`		Optimal size of the rollback segment
`HWMSIZE`	`NUMBER`		High-watermark of the rollback segment size
`SHRINKS`	`NUMBER`		Number of times the size of a rollback segment decreased
`WRAPS`	`NUMBER`		Number of times the rollback segment has wrapped
`EXTENDS`	`NUMBER`		Number of times the rollback segment size has extended
`AVESHRINK`	`NUMBER`		Average shrink size
`AVEACTIVE`	`NUMBER`		Current size of active extents, averaged over time