RE: datafiles space allocation algorithm

From: Mark W. Farnham <mwf_at_rsiz.com>
Date: Fri, 6 Oct 2006 06:24:37 -0400
Message-ID: <005f01c6e931$a1269f10$0c00a8c0@Thing1>

What manner of technology was the load? How many rows?

With the answers to those questions and a query including the file numbers for the datafiles and another with the rowid broken into the useful pieces and another adding up vsize(column_name) for each column in the table, plus an assurance that you don't have any columns that might be stored "out of line", we can answer your question. (Or the answer will become obvious to you as the query result spills out.)

Computing statistics on the table in question might also be useful if you're on a release that has statistics. You have tablespaces, so I'm pretty sure you're at least on Oracle Version 6.0, unless of course you aliased your column names in the query below.

From the data below you might only have two rows..

mwf

PS: If you want to see where Oracle puts each row and the order for sure, you're going to need the logical row number in the data you are loading. Then the answer of where Oracle stashed each row will be truly obvious if you select the useful rowid bits and the logical row number order by logical row number. (Not rownum, but an actual column added to the table containing an ordered numeric sequence. Single stride ascending integers would be most user friendly, and you might want to start with 10001 for reasons beyond the scope of this thread. Or you could start with 42.

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of amonte
Sent: Friday, October 06, 2006 4:53 AM
To: oracle-l_at_freelists.org
Subject: datafiles space allocation algorithm

Suppose we have 4 datafiles in a tablespace, when we load data into this tablespace how will Oracle assign the space? I thought it would use round-robin like but it does not.

Before load I had datafiles which looked like this:

TABLESPACE_NAME                FILE_NAME

BYTES

---------- PM_IND_T01 /u02/oradata/vmw1020/PM_IND_T01_SIMP001.dbf 16 PM_IND_T01 /u02/oradata/vmw1020/PM_IND_T01_SIMP002.dbf 16

After load it shows this:

TABLESPACE_NAME                FILE_NAME

BYTES

---------- PM_IND_T01 /u02/oradata/vmw1020/PM_IND_T01_SIMP001.dbf 272 PM_IND_T01 /u02/oradata/vmw1020/PM_IND_T01_SIMP002.dbf 1984

How does this work?

Thanks

Alex

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Received on Fri Oct 06 2006 - 05:24:37 CDT