Buffer Busy Waits (Oracle)
To display Buffer busy waits:
Alternatively, use transaction code ST04 .
The statistics presented on this screen tell you which types of Oracle block classes processes were waiting for. The number of waits for the four most common classes (data block, segment header, undo header and undo block) are usually shown with the cumulative time in milliseconds that processes were waiting.
These wait situations indicate that an Oracle process had to wait for the indicated block class which was in an inconsistent state.
See also:Monitoring the Data Buffer (Oracle)