Re: blocking enq-ss wait events

I had to look up ENQ-SS on Oracle support. That's a sort segment contention, usually encountered when SMON is really busy cleaning up a dead / killed transaction.

Oracle support has a few notes on this but the most applicable seem to stop at 11.1 .

There is one note that says to try to increase PGA_AGGREGATE_TARGET SS Sort Segment Enqueue: 'enq: SS - contention' (Doc ID 2601825.1)

Chris

On Wed, May 5, 2021 at 11:56 PM Lok P <loknath.73_at_gmail.com> wrote:

> Hi All, Need some help, we had killed one of the long running sessions
> which was running since ~8hrs+ , but after we kill that we see a lot of
> "wait for a undo record" wait events but we ignored that thinking that will
> run for sometime as because it will do rollback. But suddenly now we are
> seeing "enq-SS contention" wait event in addition to "wait for a undo
> record" and that is blocking all other application queries. So wondering
> how we should mitigate this issue?
>
> The version is 11.2.0.4 of Exadata.
>
> Regards
> Lok
>

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