Re: many seconds waiting for I/O?
- From: amonte <ax.mount@xxxxxxxxx>
- To: "Dunbar, Norman" <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 27 Jul 2007 15:13:16 +0200
I've got another going on
SID EVENT CONSISTENT_GETS WAIT_TIME SECONDS_IN_WAIT
STATE SQL_ID SEQ#
----- -------------------------- --------------- ---------- ---------------
------------------- ------------- ----------
1507 db file sequential read 214268 -1 467
WAITED SHORT TIME gd54ag7sdhxpa 48
SID EVENT CONSISTENT_GETS WAIT_TIME SECONDS_IN_WAIT
STATE SQL_ID SEQ#
----- -------------------------- --------------- ---------- ---------------
------------------- ------------- ----------
1507 db file sequential read 214285 -1 486
WAITED SHORT TIME gd54ag7sdhxpa 48
SID EVENT CONSISTENT_GETS WAIT_TIME SECONDS_IN_WAIT
STATE SQL_ID SEQ#
----- -------------------------- --------------- ---------- ---------------
------------------- ------------- ----------
1507 db file sequential read 214324 -1 513
WAITED SHORT TIME gd54ag7sdhxpa 48
The CPU usage of process keeps increasing, This is 10.2.0.2 on HP-UX. Also
the process does intensive calculations.
Alex
On 7/27/07, Dunbar, Norman <norman.dunbar@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> Hi Alex,
>
> >> If it was sql*net messages why the event shows db file
> >> sequential read?
>
> A good question.
>
> The 10g docs say that when the WAIT_TIME is non-zero that was the
> sessions last wait time. I think I may have misinterpreted that to take
> 'last' to mean 'previous' - I do apologise.
>
> Your WAIT_TIME was -1 so the wait is over and took less than one
> hundredth of a second. The wait was indeed for 'db file sequential
> read'. However, the SECONDS_IN_WAIT value is not how long the wait was
> for because WAIT_TIME was -1 and that has a specific meaning of less
> than 1 centi-second.
>
> The more I read the 10g docs, the more confused I find myself getting!
>
> For example it says that EVENT is the CURRENT wait event - what we are
> waiting on now. But WAIT_TIME of -1 or -2 says the wait is over (so in
> my book, EVENT should be null).
>
> With WAIT_TIME = zero, then we are currently waiting and therefore EVENT
> is what we are waiting on. SECONDS_IN_WAIT should be the time we have so
> far waited.
>
> With WAIT_TIME > zero then SECONDS_IN_WAIT is the time since the last
> wait started, SECONDS_IN_WAIT - WAIT_TIME / 100 is the number of active
> seconds since the last wait ended.
>
> Clear as mud ??
>
> So, what does it mean when SECONDS_IN_WAIT is high and WAIT_TIME is -1 -
> which is what your problem appears to be?
>
>
> Cheers,
> Norman.
>
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