Re: Wnnn blockers for grant operation

Appreciate the feedback.

On Mon, Aug 28, 2023, 12:40 PM Jonathan Lewis <jlewisoracle_at_gmail.com> wrote:

>
> It's certainly possible to come up with a hypothesis that could be checked:
>
> Fact: A grant operation inserts rows into at least one SYS table and if
> there is no free space in the table then a new extent would have to be
> allocate to the table.
>
> Fact: Wnnn processes are the things that handle space allocation, and
> would have to read and update a file header block to mark space in the file
> as allocated, then read and update a segment header block to attach that
> space to the segment (then, maybe, read and modify more blocks to do some
> of the work of formatting the new extent correctly).
>
>
> Possible explanation: A "library cache lock" suggests parsing activity,
> but a grant is DDL and DDL may execute on the parse call, so with a little
> glitch in timing, or some odd concurrency conditions, it's possible that
> the parse wait (library cache lock) is on the execute and waiting for the
> Wnnn to supply the space for the grant to be recorded in the data
> dictionary.
>
> Regards
> Jonathan Lewis
>
>
> On Fri, 25 Aug 2023 at 06:23, Laurentiu Oprea <laurentiu.oprea06_at_gmail.com>
> wrote:
>
>> Dear oracle community,
>>
>> Can anyone help me with an opinion on why Wnnn processes waiting for "db
>> file sequential read" will block some grant operations which are waiting
>> for "library cache lock"?
>>
>> Appreciate your answers.
>>
>

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