Home -> Mailing Lists -> Oracle-L -> Re: Oracle's automatic extent allocation (next extent) size algorithm - anyone?

Re: Oracle's automatic extent allocation (next extent) size algorithm - anyone?

From: Hemant K Chitale <hemantkchitale_at_gmail.com>
Date: Fri, 2 Apr 2021 22:04:02 +0800
Message-ID: <CAMNBsZvRGmxsLB_qzheLCndZzwuKanoWtVkV5achrjAeixzaag_at_mail.gmail.com> 








I have found Maximum Table Extent Size When Using AUTOALLOCATE (Doc ID
1302686.1)



 However, it doesn't explain when and how the RDBMS switches from 64K to 1M
and then 8M and 64M



Hemant K Chitale






On Wed, Mar 31, 2021 at 12:30 AM Jonathan Lewis <jlewisoracle_at_gmail.com>
wrote:



>

> I don't think a complete algorithm has ever been published because there

> are so many possible variations depending on whether it's a single-file or

> multi-file tablespace, depending on what's been created and dropped

> previously and what holes are arround, whether or not the insert is

> parallel or not, and whether you're creating a partitioned object.  There

> may be other complications.

>

> In the simplest case in the 8KB block size it seems to be:

> 16 extents at 64KB (8 blocks) - to get to 1MB extent

> 63 extents at 1MB (128 blocks) - to get to a total of 64MB extent

> 120 extents at 8MB (1024 blocks) - to get to 1GB

> -- after that I think it may be 64MB extents all the way, but I have a

> vague memory of someone testing to a very large segment size and finding

> 256MB as the next size.

>

>

> Regards

> Jonathan Lewis

>

>

>

>

>

> On Tue, 30 Mar 2021 at 16:47, Chris Taylor <

> christopherdtaylor1994_at_gmail.com> wrote:

>

>> Env: 12.1.0.2

>> Linux x86-64

>>

>> For Oracle segments in Locally Managed Tablespaces with *AUTOMATIC*

>> extent allocation (instead of UNIFORM extent allocation) , does anyone have

>> the algorithm that Oracle uses to determine the next extent size that is

>> based on the size of the segment?

>>

>> I used to have it where it went something like:

>>

>> IF segment > xG , then next extent = xGB

>> IF Segment > xMB then next extent = xMB

>>

>> I'm trying to find it but can't quickly locate it (because I'm not sure

>> what keywords to search for)

>>

>> Chris

>>

>



--
http://www.freelists.org/webpage/oracle-l


Received on Fri Apr 02 2021 - 16:04:02 CEST












Original text of this message