9.9 Monitoring Exadata Snapshots Using Database Statistics and Wait Events

The following table describes database specific statistics that are useful for monitoring Exadata Snapshots. The statistics are available in various dynamic performance views, including V$SYSSTAT, and may be displayed in the Global Activity Statistics or Instance Activity Statistics section of an AWR report.

Statistic	Description
physical read snap IO requests base	The number of physical I/Os on the parent or base file.
physical read snap IO requests copy	The number of physical I/Os on the snapshot file.
physical read snap bytes base	The number of bytes read from the parent or base file
physical read snap bytes copy	The number of bytes read from the snapshot file.
physical read snap IO requests new allocation	The number of new allocations on the snapshot file.
physical read snap IO requests no data	The number of physical read I/O requests for which no physical I/O is done on the child file level.

The following table describes specific database wait events that are useful for monitoring Exadata Snapshots. The wait events are visible in various dynamic performance views, including V$SESSION, V$SYSTEM_EVENT and V$SESSION_EVENT, and may be displayed in the Wait Event sections of the AWR report.

Wait Event	Description
cell physical read no I/O	The wait event appears when a read is done from a sparse disk group, and did not return any data.

The availability of a specific statistic or wait event is subject to the version of Oracle Database being used.