Re: "db file scattered read" and "db file sequential read" wait events

Roger:

These events are named for the way they store blocks into memory, not the way they're read from disk. The event "db file sequential read" corresponds to a read() call of one or more database blocks, and "db file scattered read" refers to a multi-block read issued via readv().

In February, Jeff Holt published a detailed article about this in www.hotsos.com, called "Why are Oracle's Read Events 'Named Backward'?" That particular article is available only to paid subscribers, but there's lots of free material on the site as well.

Cary Millsap
www.hotsos.com

"Roger Jackson" <rjackson_at_wire.net.au> wrote in message news:8ruk6p$2nf3$1_at_news1.wire.net.au...
> Hi.
>
> While interpreting trace files using event 10046 I have observed the
> following:
>
> During index scans the wait event is "db file sequential reads" and during
> table scans the wait event is "db file scattered reads"
>
> Does anyone know why db file sequential read events refer to random reads,
> while db file scattered reads refer to sequential reads?
>
> Should it be the other way around?
>
> Thanks in advance.
>
> Cheers,
>
> Roger.
>
>
>
Received on Thu Nov 02 2000 - 00:34:38 CST