Select sn.snap_id, sn.BEGIN_INTERVAL_TIME, sum(lc2.value - lc1.value) "redo blocks written"
From SYS.DBA_HIST_SYSSTAT lc1,
SYS.DBA_HIST_SYSSTAT lc2,
SYS.DBA_HIST_snapshot sn
where lc1.snap_id = (select max(s.snap_id)
from SYS.DBA_HIST_snapshot s
where s.snap_id < sn.snap_id
and s.instance_number = sn.instance_number
and s.dbid = sn.dbid
and s.startup_time = sn.startup_time)
and lc2.stat_name='redo blocks written'
and lc1.stat_name='redo blocks written'
and lc2.snap_id = sn.snap_id
and lc1.dbid = sn.dbid
and lc1.instance_number = sn.instance_number
and lc2.dbid = sn.dbid
and lc2.instance_number = sn.instance_number
and sn.snap_id in (&Snapshotlist)
group by sn.snap_id, sn.BEGIN_INTERVAL_TIME
order by sn.snap_id
