Oracle's system level statistics is very useful for performance track. Oracle keep on add new statistics from Oracle 8, 8i, 9i, 10g to 11g. The key is how to display the statistics value.
SQL> SELECT name, value FROM V$SYSSTAT WHERE STATISTIC# IN (54,120,56);
NAME VALUE
------------------------------ ----------
physical reads 2373
physical reads direct 39
physical reads direct (lob) 0
If you directly query the value directly from this view, it's not so useful.
20:10:24 SQL> select name,value from v$sysstat where statistic#=54;
NAME VALUE
------------------------------ ----------
physical reads 3340
......
20:10:36 SQL> select name,value from v$sysstat where statistic#=54;
NAME VALUE
------------------------------ ----------
physical reads 6371
By query two times, we found that there is 3031 (6371 - 3340) blocks physical reads in 12 seconds (20:10:24 to 20:10:36). With this information, it did tell us something about the Oracle database.
www.AnySQL.net Exec BGets RReq Read Writ Redo ...
11/27-20:15:47 54 206 15 15 0 0 ...
11/27-20:15:57 196 718 41 41 0 664 ...
11/27-20:16:07 64 637 19 61 0 6192 ...
11/27-20:16:17 17 16 0 0 0 0 ...
11/27-20:16:27 17 13 0 0 0 0 ...
11/27-20:16:37 16 6 0 0 0 0 ...
By run oramon utility, we will get the changed value of some important statistics at 10 seconds frequency, so when you hit a load strike or high load situation, you can analyze these data and know what database are doing during that time (Exec=execute count, BGets=consistent gets, RReq=read requests, Read=physical reads, Writ=physical writes, Redo=redo size, ...).