Re: Mysterious high consistent gets;

Unfortunately the data modifications is quite small and not many sessions writing into the database. Here is one of the AWR, load profile sections look like.

Load Profile                    Per Second   Per Transaction  Per Exec  Per
Call
~~~~~~~~~~~~~~~            ---------------   --------------- ---------
---------
             DB Time(s):               3.9               0.4      0.02
0.00
              DB CPU(s):               3.8               0.4      0.01
0.00
      Background CPU(s):               0.2               0.0      0.00
0.00
      Redo size (bytes):          63,873.2           6,606.3
  Logical read (blocks):          56,422.7           5,835.7
          Block changes:             271.0              28.0
 Physical read (blocks):           1,501.5             155.3
Physical write (blocks):              38.4               4.0
       Read IO requests:              15.5               1.6
      Write IO requests:               4.2               0.4
           Read IO (MB):              11.7               1.2
          Write IO (MB):               0.3               0.0
           IM scan rows:               0.0               0.0
Session Logical Read IM:
 RAC GC blocks received:              17.5               1.8
   RAC GC blocks served:              41.7               4.3
             User calls:           1,268.3             131.2
           Parses (SQL):              89.2               9.2
      Hard parses (SQL):               0.8               0.1
     SQL Work Area (MB):               9.7               1.0
                 Logons:               2.1               0.2
         Executes (SQL):             255.8              26.5
              Rollbacks:               0.0               0.0
           Transactions:               9.7

            Buffer Nowait %:  100.00       Redo NoWait %:  100.00
            Buffer  Hit   %:   99.93    In-memory Sort %:  100.00
            Library Hit   %:   99.13        Soft Parse %:   99.16
         Execute to Parse %:   65.13         Latch Hit %:   99.95
Parse CPU to Parse Elapsd %:   80.77     % Non-Parse CPU:   99.50
          Flash Cache Hit %:    0.00

                                           Total Wait       Wait   % DB Wait
Event                                Waits Time (sec)    Avg(ms)   time

------------------------------ ----------- ---------- ---------- ------
--------
DB CPU                                          13.8K              97.4
log file sync                       48,284      141.6       2.93    1.0
Commit
rdbms ipc reply                    299,603      121.7       0.41     .9
Other
direct path read                    13,064      114.4       8.76     .8
User I/O
DFS lock handle                     37,522       30.4       0.81     .2
Other
db file scattered read               4,302       27.4       6.37     .2

Thanks

On Tue, Jun 19, 2018 at 3:16 AM, Tim Gorman <tim.evdbt_at_gmail.com> wrote:

> There is likely a big difference in overall conditions between when you
> run the query yourself versus how it is running out "in the wild" by
> LoadRunner.
>
> For example, in LoadRunner, are you also having other sessions (or the
> same sessions) also performing data modification on the table(s) that this
> query is scanning?
>
> If so, then a fair portion of your "consistent gets" are likely coming
> from undo segments, not from table/index segments, as the query executed
> under LoadRunner is having to rebuild the consistent image at the
> point-in-time when the query began while updates/deletes/merges are
> happening concurrently.
>
> In contrast, when you are running the query by yourself for testing with
> autotrace and tkprof, there are probably no modifications to the table(s)
> going on, so "consistent gets" are very simple and relatively inexpensive.
>
>
>
>
> On 6/18/18 12:48, Ashish Lunawat wrote:
>
>> Hi, I have a query which when run through autotrace and tkprof shows me
>> about 50,000 gets. But the same query when shot as a part of loadrunner
>> performance testing causes about 1.2 million consistent gets as seen in the
>> AWR report. How is this possible?
>>
>> The database is running on a 2 node RAC with each node having 32 cores.
>> Tkprof shows this query takes about .8 seconds and causes 50K consistent
>> gets while when shot through loadrunner it, causes both the RAC nodes to go
>> as much as 100% CPU. When monitoring session waits I can see that there is
>> a hot block contention happening on a table with about 19K rows and an
>> index on this table. This query is responsible for about 94% of the gets
>> and thus high cpu utilization.
>>
>> Any clues how to troubleshoot this issue?
>>
>> Thanks
>> Regards,
>> Ashish
>>
>>
>

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