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Don Burleson Blog 







Plotting Oracle CPU Utilization percentage

Oracle Database Tips by Donald BurlesonApril 20,  2015

Plotting Oracle CPU Utilization percentage

Oracle does not exist in a vacuum, and you need to monitor external influences such as CPU enqueues (when the runqueue exceeds the number of [processors on your server), plus RAM swapping, network latency and disk enqueues.

For plotting CPU, we compute the deltas of "busy" and "idle" time and use "busy / (busy + idle)" to get a CPU utilization percentage.

Please note, some of the OS statistics may be difficult, as they differ based on every server operating system, but the CPU BUSY and CPU IDLE time are constant across OS implementations.

Charting CPU utilization over time

select 'OS Busy Time' series, to_char(snaptime, 'yyyy-mm-dd hh24') snap_time, round(busydelta / (busydelta + idledelta) * 100, 2) "CPU Use (%)"
from (
select s.begin_interval_time snaptime,
os1.value - lag(os1.value) over (order by s.snap_id) busydelta,
os2.value - lag(os2.value) over (order by s.snap_id) idledelta
from dba_hist_snapshot s, dba_hist_osstat os1, dba_hist_osstat os2
s.snap_id = os1.snap_id and s.snap_id = os2.snap_id
and s.instance_number = os1.instance_number and s.instance_number = os2.instance_number
and s.dbid = os1.dbid and s.dbid = os2.dbid
and s.instance_number = (select instance_number from v$instance)
and s.dbid = (select dbid from v$database)
and os1.stat_name = 'BUSY_TIME'
and os2.stat_name = 'IDLE_TIME'
and s.snap_id between &beginsnap and &endsnap

For more scripts for plotting Oracle metrics, see The Oracle script collection.



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