doc

    Name:    pingwrts.sql

    Author:  Mark Gurry

    The following query shows the percentage of physical writes to the
    database that have been due to pings.

#

SELECT(a.value / b.value) * 100
  FROM v$sysstat a, v$sysstat b
 WHERE a.name = 'DBWR cross instance writes'    
    AND b.name  = 'physical writes';