FAQ
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.

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  • Bobak, Mark at Jul 10, 2008 at 7:38 pm
    Check this out:
    http://download.oracle.com/docs/cd/B19306_01/server.102/b15658/appa_aix.htm#sthref782

    --
    Mark J. Bobak
    Senior Database Administrator, System & Product Technologies
    ProQuest
    789 E. Eisenhower, Parkway, P.O. Box 1346
    Ann Arbor MI 48106-1346
    +1.734.997.4059 or +1.800.521.0600 x 4059
    mark.bobak_at_proquest.com
    www.proquest.com<http://www.proquest.com>
    www.csa.com<http://www.csa.com>

    ProQuest...Start here.

    From: oracle-l-bounce_at_freelists.org 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

    --
    http://www.freelists.org/webpage/oracle-l
  • Jason Heinrich at Jul 10, 2008 at 8:34 pm
    Good information, but I don't think it applies to this system. I found out
    that the AIX version is 4.2, so the "-T O" option doesn't exist for creating
    a raw volume. Also, we couldn't find the Oracle "offset" command that was
    mentioned.

    I've been digging through the 7.3.4 documentation on tahiti, but haven't
    found anything useful yet. Any other ideas?

    On Thu, Jul 10, 2008 at 2:38 PM, Bobak, Mark
    wrote:
  • Bobak, Mark at Jul 10, 2008 at 8:48 pm
    Argh, I forgot you're on 7.3.4, the command probably doesn't exist on 7.3.4.....

    Hmm...sorry, I can't help. You may want to check w/ your sysadmin for the offset.

    -Mark

    --
    Mark J. Bobak
    Senior Database Administrator, System & Product Technologies
    ProQuest
    789 E. Eisenhower, Parkway, P.O. Box 1346
    Ann Arbor MI 48106-1346
    +1.734.997.4059 or +1.800.521.0600 x 4059
    mark.bobak_at_proquest.com
    www.proquest.com<http://www.proquest.com>
    www.csa.com<http://www.csa.com>

    ProQuest...Start here.

    From: jheinrich_at_heinrichfamily.com On Behalf Of Jason Heinrich
    Sent: Thursday, July 10, 2008 4:34 PM
    To: Bobak, Mark
    Cc: oracle-l
    Subject: Re: AIX raw device offset

    Good information, but I don't think it applies to this system. I found out that the AIX version is 4.2, so the "-T O" option doesn't exist for creating a raw volume. Also, we couldn't find the Oracle "offset" command that was mentioned.

    I've been digging through the 7.3.4 documentation on tahiti, but haven't found anything useful yet. Any other ideas?

    On Thu, Jul 10, 2008 at 2:38 PM, Bobak, Mark > wrote:

    Check this out:

    http://download.oracle.com/docs/cd/B19306_01/server.102/b15658/appa_aix.htm#sthref782

    --
    Jason Heinrich

    --
    http://www.freelists.org/webpage/oracle-l
  • Mark W. Farnham at Jul 10, 2008 at 9:55 pm
    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.



    Regards,



    mwf

    From: oracle-l-bounce_at_freelists.org
    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 at Jul 10, 2008 at 10:36 pm
    It's not our system, it's a customer's that we're supporting. An IBM
    support article (http://tinyurl.com/6jzeaf) indicates that the header is 4K,
    but I'll pass your suggestion on to my coworker who's working with the
    customer. Thanks.
    On Thu, Jul 10, 2008 at 4:55 PM, Mark W. Farnham wrote:

    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.



    Regards,



    mwf
    --
    Jason Heinrich

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

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