Amount of space used by a segment changes when datafile size changed in ASSM tablespace

From: Peter Hitchman <pjhoraclel_at_gmail.com>
Date: Mon, 8 Apr 2013 16:31:19 +0100
Message-ID: <CAPMSPxOmSddOLm4Vyj+y12yod2g5iFoVVcKzMdvMnzRWOXtqSw_at_mail.gmail.com>



Oracle Enterprise Edition 11.1.0.7.5
Linux 64 bit RHL 4.5

I have a question about space allocation in ASSM tablespaces.

I am using a 8KB block size and 8MB extents.

I started off with a single extent segment reported as using 9MB according to OEM, I checked dba_data_files and dba_free_space_coalesced and the sum of bytes used minus the total free bytes used agreed this figure.

When I increased the file size from 33MB to 40MB, the amount of space used is reported as 16MB.
When I shrink the file to 33MB, the amount of space used goes back down to 9MB.
When I shrink the file to 32MB the amount of space used goes up to 16MB.

I feel I should understand this, but it is escaping me.

Regards

Pete

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Received on Mon Apr 08 2013 - 17:31:19 CEST

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