RE: AIX raw device offset

From: Mark W. Farnham <>
Date: Thu, 10 Jul 2008 17:55:59 -0400
Message-ID: <031a01c8e2d7$bdb8f3c0$>

dd from an existing raw volume to a regular file on a JFS volume for a file system you don't care about (possibly created for the purpose). Then od the file and look for the offset where you see a typical Oracle file header. I'm pretty sure Oracle's files are 1 database block size bigger than you asked for as well, so make sure you have at least offset plus file size you think you have plus 1 db block size available on the raw device you prepare to receive the new file. (That's for it to work at all. Getting the header aligned in a good way compared to the underlying physical storage that is being presented by the volume manager to the OS is another matter.)  

I won't even pry into why you're still using 7.3.x.  

By the way, unless this is an nth file of a multi file tablespace or a huge tablespace, I'd think seriously about creating a new tablespace the way you want it, copying the data you want to keep, and then dropping the old tablespace including contents. If it is a big tablespace that is probably a lot of i/o, but if you've got the space to do it it will be a lot safer. Even the dinosaurs who used to do this stuff frequently are rusty at doing it by now, and if I recall correctly some OS documents were at a lower standard of exactness than the general Oracle documentation.  



From: [] On Behalf Of Jason Heinrich
Sent: Thursday, July 10, 2008 3:13 PM
To: oracle-l
Subject: AIX raw device offset  

Oracle 7.3.3
Oracle Parallel Server

A coworker of mine needs to move a datafile that was accidentally created on a local JFS volume to a shared raw device. He's planning on using dd. Can anyone tell me what the correct offset is for the start of the datafile on an AIX raw device? It's my understanding that AIX writes its own info to the first x bytes of the device, so the Oracle file header needs to start after that.

Sorry, I don't know what version of AIX this is offhand. If that matters, let me know and I'll try to find out.


Jason Heinrich

-- Received on Thu Jul 10 2008 - 16:55:59 CDT

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