Re: Reads from Control file under "IOStat by Filetype summary"
Date: Thu, 29 May 2014 18:16:06 +0530
Message-ID: <CALQThVctigt7xMt3eyOZVC-konyqx4pgG=uBScm0DV0Tk2UFeQ_at_mail.gmail.com>
Dear All,
Thanks a lot for your inputs.
- I have requested the DBA team to provide me queries that had wait events "control file sequential read", "db file scattered read" and "direct path read"
- As Jonathan hinted, the "archive_lag_target" is set to 5 minutes.
- I have also requested the team to share if any monitoring scripts are being executed against the database.
While I wait for the inputs, I have 1 more question. How to derive balance value for "arhive_lag_target" parameter. For this particular scenario the environment has dataguard configured.
Warm Regards,
Vijay Sehgal.
On Thu, May 29, 2014 at 4:59 PM, <coskan_at_gmail.com> wrote:
> Apart from what Timur and Jonathan already said, If you want to guess it
> can be monitoring script(most probably space checker) with an inefficient
> plan or unnecessary intervals
>
> *From: *Timur Akhmadeev
> *Sent: *Thursday, 29 May 2014 14:25
> *To: *vijaysehgal21_at_gmail.com
> *Reply To: *timur.akhmadeev_at_gmail.com
> *Cc: *ORACLE-L
> *Subject: *Re: Reads from Control file under "IOStat by Filetype summary"
>
> Hi Vijay
>
> You may try to find SQL id and SQL plan id from ASH for 'control file
> sequential read' events and go from there
> Something like
>
> select sql_id, sql_plan_line_id, count(*)
> from v$ash
> where event = ...
> Group by ...
>
> It may not give you anything though and then you may need to trace some
> sessions to find the definitive answer
>
> On Thursday, May 29, 2014, vijay sehgal <vijaysehgal21_at_gmail.com> wrote:
>
>> Dear Experts,
>>
>> Below are few sections from AWR report. The server is running Linux x86
>> 64 bit, 11.2.0.3.0 with 24 CPUs, 12 Cores and 2 Sockets.Physical Memory is
>> 22GB.
>>
>> The AWR reports is for 3 hours.
>>
>>
>> ----------------------------------------------------------------------------
>> Per Second Per Transaction Per Exec Per Call
>>
>> ----------------------------------------------------------------------------
>> DB Time(s): 0.2 0.6 0.01 0.08
>> DB CPU(s): 0.1 0.1 0 0.02
>> Redo size: 1,371.50 3,402.50
>> Logical reads: 983.5 2,439.90
>> Block changes: 4.6 11.3
>> Physical reads: 869.8 2,157.90
>> Physical writes: 1.6 4.1
>> User calls: 2.9 7.2
>> Parses: 0.7 1.6
>> Hard parses: 0 0.1
>> W/A MB processed: 0.4 0.9
>> Logons: 0 0.1
>> Executes: 21.4 53.1
>> Rollbacks: 0 0
>> Transactions: 0.4
>>
>>
>>
>> -----------------------------------------------------------------------------------------------------------
>> Event Waits Time(s) Avg wait
>> (ms) % DB time Wait Class
>>
>> direct path read 320,496 838 3
>> 33.45 User I/O
>> db file scattered read 170,986 744 4
>> 29.72 User I/O
>> DB CPU 581 23.19
>> control file sequential read 48,036 320 7
>> 12.77 System I/O
>> db file sequential read 23,789 42 2
>> 1.68 User I/O
>>
>> -----------------------------------------------------------------------------------------------------------
>>
>> IOStat by Function summary
>>
>>
>> -----------------------------------------------------------------------------------------------------------
>> Function Name Reads: Reqs per Data per Writes: Reqs per Data
>> per Waits: Avg Tm(ms)
>> Data sec sec Data sec
>> sec Count
>>
>> -----------------------------------------------------------------------------------------------------------
>> Direct Reads 52.3G 40.2 4.95684 0M 0
>> 0M 0
>> Others 31.7G 8.94 2.99843 620M 3.38
>> 0.057357 109.4K 3.01
>> Buffer Cache Reads 19.4G 18.8 1.8349 0M 0
>> 0M 202.6K 3.52
>> LGWR 329M 1.96 0.030436 318M 3.79
>> 0.029419 38.7K 0.56
>> DBWR 0M 0 0M 133M 1.39
>> 0.012304 0
>> Direct Writes 0M 0 0M 3M 0.04
>> 0.000277 0
>> TOTAL: 103.7G 69.91 9.82061 1G 8.59
>> 0.099358 350.7K 3.03
>>
>> -----------------------------------------------------------------------------------------------------------
>>
>> IOStat by Filetype summary
>>
>> -----------------------------------------------------------------------------------------------------------
>> Filetype Name Reads: Reqs per Data per Writes: Reqs per Data
>> per Small Read Large Read
>> Data sec sec Data sec
>> sec
>>
>> -----------------------------------------------------------------------------------------------------------
>> Data File 71.7G 59.1 6.79266 138M 1.43
>> 0.012766 3.3 5.27
>> Control File 31.9G 10.31 3.02369 834M 4.94
>> 0.077155 0.26 9.02
>> Flashback Log 19M 0.01 0.001757 46M 0.06
>> 0.004255 0.2 40.94
>> Log File 19M 0.06 0.001757 37M 2.13
>> 0.003422 0.19 27.45
>> Archive Log 0M 0 0M 18M 0
>> 0.001665
>> Other 9M 0.42 0.000832 2M 0.02
>> 0.000185 0.11
>> Temp File 0M 0.01 0M 0M 0 0M
>> 0.75
>> TOTAL: 103.7G 69.91 9.8207 1G 8.59
>> 0.099451 1.77 5.48
>>
>> -----------------------------------------------------------------------------------------------------------
>>
>> I have a few questions with respect to above, if further details are
>> required please revert and I would provide the same.
>>
>> Log switch during this period was 12 per hour (derived from AWR). I have
>> raised this with the team.
>>
>> 1. IOStat by Filetype shows reads from control file as 31.9G. I am not
>> sure why would database be reading 31.9 GB from control file? (There was no
>> backup being performed during this interval).
>>
>> 2. How do I investigate this further, I don't have access to production
>> box. I will have to give queries to DBA team to get the details. So any
>> pointed queries, would be helpful.
>>
>> 3. Would Direct Path Reads be causing this? if yes how do I dig more
>> information to correlate these.
>>
>> 4. I tried to do some search on the wait event "control file sequential
>> read" and found that using Subquery factoring could cause "control file
>> sequential reads". But the issue was fixed in 11.1.7.0.1. Are there any
>> other known issues which could cause this problem.
>>
>> Your help is much appreciated.
>>
>> Warm Regards,
>> Vijay Sehgal
>>
>
>
> --
> Regards
> Timur Akhmadeev
>
>
>
-- http://www.freelists.org/webpage/oracle-lReceived on Thu May 29 2014 - 14:46:06 CEST