Re: many seconds waiting for I/O?

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_at_environment-agency.gov.uk> 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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