Exchange not updating busy
One of the most confounding problems with Oracle is the resolution of buffer busy wait events.Buffer busy waits are common in an I/O-bound Oracle system, as evidenced by any system with read (sequential/scattered) waits in the top-five waits in the Oracle STATSPACK report, like this: The main way to reduce buffer busy waits is to reduce the total I/O on the system.
While session one awaits the disk read to complete, other sessions scanning the same index soon catch up to session one and want the same block currently being read from disk. waiting for the buffer blocks that are being read from disk.The v$session_wait performance view, shown below, can give some insight into what is being waited for and why the wait is occurring.Once the segment is identified, the v$segment_statistics performance view facilitates real-time monitoring of segment-level statistics.The following rules of thumb may be useful for resolving each of the noted contention situations: "buffer busy wait w/ P3=0 means the buffer is locked because the contents are being read from disk by another session.
(See MOSC Doc ID 34405.1 for more details.) This is most likely caused by multiple, concurrent sessions that are reading the same table or set of tables.The only way to bring it all back, is to either restart all services, just the AD Topology or restart the entire server.