Re: High waits/Timeouts - log file parallel write

Hi Tom,

The 'log file parallel write' waits affect LGWR only. They do not affect the performance of user processes directly (although they do impact somewhat on your 'log file sync' wait duration). The number of timeouts is influenced by your use of asynchronous I/O and by how often LGWR is posted by user processes. It is not a useful indicator of performance problems.

I think you should be more concerned about the 'control file parallel write' waits that are probably affecting user processes directly.

@   Regards,
@   Steve Adams
@   http://www.ixora.com.au/         - For DBAs
@   http://www.christianity.net.au/  - For all

TP wrote:
> Hello all,
>
> I seeing high Waits, Timeouts from one the
> problem instance.
>
> Top 5 Timed Events
> ~~~~~~~~~~~~~~~~~~
> % Total
> Event
> Waits Time (s) Ela Time
> --------------------------------------------
> ------------ ----------- --------
> CPU time
> 8 40.51
> control file parallel write
> 642 5 25.56
> db file sequential read
> 343 2 9.40
> log file parallel write
> 9,697 2 7.99
> log file sync
> 425 1 5.69
>
> -------------------------------------------------------------
> ^LWait Events for DB: C3PO Instance: C3PO
[snip]
> Avg
>
> Total Wait wait Waits
> Event Waits
> Timeouts Time (s) (ms) /txn
> ---------------------------- ------------
> ---------- ---------- ------ --------
> control file parallel write 642
> 0 5 8 1.4
> db file sequential read 343
> 0 2 6 0.7
> log file parallel write 9,697
> 8,429 2 0 21.1
> log file sync 425
> 0 1 3 0.9

[snip]
>
> -----------------------------------------
> It seems like I'm having some issue with the LGWR
> "log file parallel write" (timeouts).
> Can you suggest and/or provide some
> recommendations? The DB version is 9205 on
> Solaris 2.9.
>
> Thanks in advance!
> Tom

[snip]

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