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AWR: How to interpret DB Time if CPU% and Events% are small

TimWong765Mar 4 2016 — edited Mar 13 2016

I have trouble interpreting the following AWR.

DB Time is 82.85 min within a 1h snapshot interaval.

  • If I check CPU: 1447sec/60 = 24min ahve be consumed. Around 30% of DB Time
  • Top Timed Events are reads with 273sec + 168sec + 34sec = 475sec = 8min. Just a small percentage of DB Time

So what has the database done in the remaining 82min -24min - 8min = 50min?

DB Name         DB Id    Instance     Inst Num Startup Time    Release     RAC

------------ ----------- ------------ -------- --------------- ----------- ---

                                              1 11-Jan-15 19:09 11.2.0.3.0  NO


Host Name        Platform                         CPUs Cores Sockets Memory(GB)

---------------- -------------------------------- ---- ----- ------- ----------

xxxxxxxxx        AIX-Based Systems (64-bit)          8     2               8.00

              Snap Id      Snap Time      Sessions Curs/Sess

            --------- ------------------- -------- ---------

Begin Snap:     20849 03-Mar-16 06:00:43        50       2.4

  End Snap:     20850 03-Mar-16 07:00:46        48       2.0

   Elapsed:               60.04 (mins)

   DB Time:               82.85 (mins)

Load Profile              Per Second    Per Transaction   Per Exec   Per Call

~~~~~~~~~~~~         ---------------    --------------- ---------- ----------

      DB Time(s):                1.4                3.7       0.00       0.00

       DB CPU(s):                0.4                1.1       0.00       0.00

       Redo size:        2,454,102.5        6,592,682.0

   Logical reads:           30,625.6           82,272.5

   Block changes:            5,082.7           13,654.0

  Physical reads:              875.1            2,350.9

Physical writes:              625.5            1,680.4

      User calls:            1,166.3            3,133.2

          Parses:                7.5               20.2

     Hard parses:                2.1                5.5

W/A MB processed:                5.0               13.5

          Logons:                0.1                0.4

        Executes:            5,213.9           14,006.4

       Rollbacks:                0.0                0.0

    Transactions:                0.4

Instance Efficiency Percentages (Target 100%)

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

            Buffer Nowait %:  100.00       Redo NoWait %:  100.00

            Buffer  Hit   %:   98.49    In-memory Sort %:   99.98

            Library Hit   %:   99.89        Soft Parse %:   72.55

         Execute to Parse %:   99.86         Latch Hit %:   99.99

Parse CPU to Parse Elapsd %:   28.99     % Non-Parse CPU:   98.94

Top 5 Timed Foreground Events

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

                                                           Avg

                                                          wait   % DB

Event                                 Waits     Time(s)   (ms)   time Wait Class

------------------------------ ------------ ----------- ------ ------ ----------

DB CPU                                            1,447          29.1

db file scattered read               82,816         273      3    5.5 User I/O

db file sequential read             383,558         168      0    3.4 User I/O

direct path read temp                25,244          34      1     .7 User I/O

library cache lock                      438           8     19     .2 Concurrenc

Host CPU (CPUs:    8 Cores:    2 Sockets: )

~~~~~~~~         Load Average

               Begin       End     %User   %System      %WIO     %Idle

           --------- --------- --------- --------- --------- ---------

                0.61      1.18      10.1       4.0       0.5      85.9

Time Model Statistics            DB/Inst: SABADWH/SABADWH  Snaps: 20849-20850

-> Total time in database user-calls (DB Time): 4971.2s

-> Statistics including the word "background" measure background process

   time, and so do not contribute to the DB time statistic

-> Ordered by % or DB time desc, Statistic name

Statistic Name                                       Time (s) % of DB Time

------------------------------------------ ------------------ ------------

sql execute elapsed time                              3,701.4         74.5

DB CPU                                                1,446.6         29.1

PL/SQL execution elapsed time                           101.6          2.0

parse time elapsed                                       53.6          1.1

hard parse elapsed time                                  28.7           .6

RMAN cpu time (backup/restore)                            4.8           .1

PL/SQL compilation elapsed time                           3.7           .1

hard parse (sharing criteria) elapsed time                3.2           .1

hard parse (bind mismatch) elapsed time                   3.1           .1

failed parse elapsed time                                 1.1           .0

repeated bind elapsed time                                0.5           .0

connection management call elapsed time                   0.4           .0

sequence load elapsed time                                0.1           .0

inbound PL/SQL rpc elapsed time                           0.0           .0

DB time                                               4,971.2

background elapsed time                                 667.9

background cpu time                                      73.0

          -------------------------------------------------------------

This post has been answered by Franck Pachot on Mar 10 2016
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Locked on Apr 10 2016
Added on Mar 4 2016
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