6.3.4.2 Monitoring Exadata Smart Flash Log Using Database Statistics and Wait Events

The following table describes various database statistics that are useful for monitoring redo write and Exadata Smart Flash Log performance. 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
redo write size count (4KB) redo write size count (8KB) redo write size count (16KB) redo write size count (32KB) redo write size count (64KB) redo write size count (128KB) redo write size count (256KB) redo write size count (512KB) redo write size count (1024KB) redo write size count (inf)	Number of redo writes where the redo write size is smaller than the size indicated in parenthesis. For example, redo write size count (4KB) includes redo writes smaller than 4 KB in size, and redo write size count (inf) includes redo writes over 1 MB in size.
redo writes	Total number of writes to the redo log files by the Oracle Database log writer (LGWR) process(es).

The following table describes database wait events that are useful for monitoring redo write and Exadata Smart Flash Log performance. 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
log file parallel write	The Oracle Database log writer (LGWR) process waits on this event when it is waiting for the completion of writes to the redo log file. Efficient use of Exadata Smart Flash Log is indicated by comparatively lower time waiting on this event.

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