ROLLBACK EXTENDING AND SHRINKAGE NOTES:
Rollback Segment - Name of rollback segment.
Seg# - Rollback segment number.
Size - Size in bytes of the rollback segment.
OptSize - Optimal size of rollback segment.
HWM - High Water Mark of rollback segment size.
Extends - Number of times rollback segment was extended to have a new extent.
Wraps - Number of times rollback segment wraps from one extent to another.
Shrinks - Number of times rollback segment shrank, eliminating one or more additional extents each time.
Average Shrink - Total size of freed extents divided by number of shrinks.
Average Active - Current average size of active extents, where "active" extents have uncommitted
transaction data.
Status - ONLINE if the segment is online, or PENDING OFFLINE if the segment is going offline but some active
(distributed) transactions are using the rollback segment. When the transaction(s) complete, the segment goes OFFLINE.