Base Statistics, Metrics, and Statistics
Levels
The modify_snapshot_settings
procedure can be run to control the behavior of snapshots. The
retention parameter determines how much AWR information
is retained by the database. On a typical system, AWR
collections require 200 MB to 300 MB of space if the data is
kept for seven days. The default is seven days (10080) and the
minimum is one day.
The space consumption depends mainly on the
number of active sessions in the system, so adjust accordingly.
If the retention value is set to 0, it will disable the
automatic purging. If AWR detects that SYSAUX is out of space,
it automatically deletes the oldest set of snapshots and reuses
the space. Alerts will be sent to the DBA using the designated
communication methods (email/pager) to inform them that SYSAUX
is running out of space.
The interval parameter determines
the frequency of snapshot generation. The minimum value is 10
minutes and the default is 60 minutes. Setting it to 0 will
disable the automatic capturing of snapshots. Typical values are
10, 20, 30, 60, 120, etc.
Similar to STATSPACK, the AWR has a report generation mechanism
to produce summary reports on statistics stored in the AWR
repository. The analysis is done on statistics over a period of
time and the reports are generated using the script
awrrpt.sql in the $ORACLE_HOME/rdbms/admin directory. The
script displays all the AWR snapshots available and prompts for
options on how and where the reports are to be generated. The
awrrpt.sql script produces two kinds of output. The default
is HTML format with hyperlinks, and the other is in text format
similar to STATSPACK reports. When the script is run, it prompts
for the format of the report and the report name.
