SAR (System Buffer Usage)

To monitor the system's buffer activity (not Oracle's buffer cache).

# sar -b 10 5

It provides the number of transfers per second between system buffers and block devices.

Bread/s, bwrit/s -No. of physical I/O. Gives overall write activity on server.
Lread/s, lwrit/s -No. of reads and writes from and to system’s buffer cache.
Pread/s, pwrit/s -No. of I/O on raw devices.
%rcache, %wcache-Buffer cache hit ratio for read and write requests. (100* (lread –bread)/lread )

Inference

• %rcache > 90% indicates the potential for bad disk I/O.
• %wcache < 70% indicates the potential for bad disk I/O.

Thanks