Re: How does Oracle determine how much to extend autoextend datafiles?

On 2019/03/14 17:59, Tanel Poder wrote:

> Oracle tries to be proactive with tablespace extension (and even some segments' extention - securefiles for example). That's why the Space Management COordinator (SMCO) and its worker slaves (Wnnn) exist. So assuming that there was no user activity (like creating and later dropping/purging a large table), I'd say the SMCO process got a little too proactive with extending datafiles. Maybe you'll find some traces or warnings in alert log or the SMCO tracefile.
>
> There's a _enable_space_preallocation parameter that controls this and also plenty of MOS notes:
>
> * SMCO (Space Management Coordinator) For Autoextend On Datafiles And How To Disable/Enable (Doc ID 743773.1)
> * AUTOEXTEND Grows To Full Size Without Reason (Doc ID 1459097.1)
> * Master Note: Overview of Oracle Segment Storage (Doc ID 1491960.1) - _search for SMCO_

There's no smco tracefile, other than an unrelated incident more than a week before my recent upgrade. And nothing in the alert log, other than the notification of the datafile extends.

Looks like I have some homework to do. But at least now I have some idea of where to start looking. :)

Thanks much, Tanel!
Rich

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