FAQ
So, the situation is this, I have a tablespace with about 600GB of free
space (spread out in about 80 datafiles). The entire database itself has
about 2TB and we need to copy it to another server. The problem is that we
have 1.5TB allocated in the ASM instance in the destination server. We
wanted to use RMAN, but the database won't fit. We could use export/import
but it would take too long and we don't have anywhere to store the export.

Someone pointed to me that RMAN was capable of duplicating only the used
blocks... I researched a lot but I couldn't find it... so I'm either looking
in the wrong place or that someone was wrong. (there is also the possibility
that I'm very sleepy).

I know rman can compress backups and that it only backs up used blocks (when
doing a backupset anyway) but I think duplicate just... duplicates... I
don't think it resizes and moves stuff around.

Anyway... I think we will have to go with datapump for this one (we are on
11g anyway), but I was just wondering if I was missing a key feature in
rman...

thanks
Alan.-

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  • Allen, Brandon at Jun 28, 2011 at 4:10 pm
    I've never heard of such a feature, but would also be interested to hear if someone else knows about it. I'm guessing maybe the person that mentioned this to you was just confused about the fact that RMAN will only write used blocks to the backup set, but when it restores the backup, it fills in those unused blocks again. I'm pretty sure that duplicate works exactly the same as a regular restore - it just automates the other stuff for you like creating the controlfile, renaming datafiles, setting the new DBID, etc. I agree that it sounds like you'll need to use data pump, unless maybe there is only a subset of tablespaces that you need - then you could use transportable tablespaces just for those, and you can use RMAN to create the transportable tablespaces if required to avoid downtime in the source database.

    Regards,
    Brandon

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  • Vishal Gupta at Jun 28, 2011 at 4:15 pm
    This is my understanding as well. RMAN will decompress the unused blocks and create an block for block copy on target database. I have not read/heard of RMAN being able to restore only used block.

    Regards,
    Vishal Gupta
    Email - vishal_at_vishalgupta.com
    Blog - http://blog.vishalgupta.com
    Twitter - http://www.twitter.com/vishalgupta77
    LinkedIn - http://uk.linkedin.com/in/vishalgupta77
    On 28 Jun 2011, at 17:10, Allen, Brandon wrote:

    I�ve never heard of such a feature, but would also be interested to hear if someone else knows about it. I�m guessing maybe the person that mentioned this to you was just confused about the fact that RMAN will only write used blocks to the backup set, but when it restores the backup, it fills in those unused blocks again. I�m pretty sure that duplicate works exactly the same as a regular restore � it just automates the other stuff for you like creating the controlfile, renaming datafiles, setting the new DBID, etc. I agree that it sounds like you�ll need to use data pump, unless maybe there is only a subset of tablespaces that you need � then you could use transportable tablespaces just for those, and you can use RMAN to create the transportable tablespaces if required to avoid downtime in the source database.

    Regards,
    Brandon


    Privileged/Confidential Information may be contained in this message or attachments hereto. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.
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  • Rajendra.pande_at_ubs.com at Jun 28, 2011 at 4:17 pm
    I don't believe there is any such feature. Notice the words "I believe"
    :-)

    What I believe is available in 11G is that RMAN is capable of backing up
    only used blocks

    But in 1 iTB file if only 200M is used then my understanding will be
    that somehow magically the output file will still be 1TB even though
    only 200MB was backed up.

    Of course I have not tested it yet.



    Thanks



    From: oracle-l-bounce_at_freelists.org
    On Behalf Of Guillermo Alan Bort
    Sent: Tuesday, June 28, 2011 11:51 AM
    To: oracle-l-freelists
    Subject: RMAN duplicate only used blocks?



    So, the situation is this, I have a tablespace with about 600GB of free
    space (spread out in about 80 datafiles). The entire database itself has
    about 2TB and we need to copy it to another server. The problem is that
    we have 1.5TB allocated in the ASM instance in the destination server.
    We wanted to use RMAN, but the database won't fit. We could use
    export/import but it would take too long and we don't have anywhere to
    store the export.

    Someone pointed to me that RMAN was capable of duplicating only the used
    blocks... I researched a lot but I couldn't find it... so I'm either
    looking in the wrong place or that someone was wrong. (there is also the
    possibility that I'm very sleepy).

    I know rman can compress backups and that it only backs up used blocks
    (when doing a backupset anyway) but I think duplicate just...
    duplicates... I don't think it resizes and moves stuff around.

    Anyway... I think we will have to go with datapump for this one (we are
    on 11g anyway), but I was just wondering if I was missing a key feature
    in rman...

    thanks
    Alan.-

    Please visit our website at
    http://financialservicesinc.ubs.com/wealth/E-maildisclaimer.html
    for important disclosures and information about our e-mail
    policies. For your protection, please do not transmit orders
    or instructions by e-mail or include account numbers, Social
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    personal information.
  • Niall Litchfield at Jun 28, 2011 at 4:32 pm
    The source of the quote was likely the nfs clonedb feature introduced in 11g
    (maybe R2). Kevin Closson has an intro at
    http://kevinclosson.wordpress.com/2010/12/23/oracle-database-11g-direct-nfs-clonedb-feature-part-i/
    it
    is a cool feature, but probably won't help Alan.
    On Tue, Jun 28, 2011 at 5:17 PM, wrote:

    I don�t believe there is any such feature. Notice the words �I believe�
    J****

    What I believe is available in 11G is that RMAN is capable of backing up
    only used blocks****

    But in 1 iTB file if only 200M is used then my understanding will be that
    somehow magically the output file will still be 1TB even though only 200MB
    was backed up.****

    Of course I have not tested it yet.****

    ** **

    Thanks ****

    ** **
    ------------------------------

    *From:* oracle-l-bounce_at_freelists.org [mailto:
    oracle-l-bounce@freelists.org] *On Behalf Of *Guillermo Alan Bort
    *Sent:* Tuesday, June 28, 2011 11:51 AM
    *To:* oracle-l-freelists
    *Subject:* RMAN duplicate only used blocks?****

    ** **

    So, the situation is this, I have a tablespace with about 600GB of free
    space (spread out in about 80 datafiles). The entire database itself has
    about 2TB and we need to copy it to another server. The problem is that we
    have 1.5TB allocated in the ASM instance in the destination server. We
    wanted to use RMAN, but the database won't fit. We could use export/import
    but it would take too long and we don't have anywhere to store the export.

    Someone pointed to me that RMAN was capable of duplicating only the used
    blocks... I researched a lot but I couldn't find it... so I'm either looking
    in the wrong place or that someone was wrong. (there is also the possibility
    that I'm very sleepy).

    I know rman can compress backups and that it only backs up used blocks
    (when doing a backupset anyway) but I think duplicate just... duplicates...
    I don't think it resizes and moves stuff around.

    Anyway... I think we will have to go with datapump for this one (we are on
    11g anyway), but I was just wondering if I was missing a key feature in
    rman...

    thanks
    Alan.-****

    Please visit our website at
    http://financialservicesinc.ubs.com/wealth/E-maildisclaimer.html
    for important disclosures and information about our e-mail
    policies. For your protection, please do not transmit orders
    or instructions by e-mail or include account numbers, Social
    Security numbers, credit card numbers, passwords, or other
    personal information.
    --
    Niall Litchfield
    Oracle DBA
    http://www.orawin.info

    --
    http://www.freelists.org/webpage/oracle-l
  • Allen, Brandon at Jun 28, 2011 at 5:19 pm
    That is pretty cool. I'd never heard of it before. Here is the MOS Doc ID for more info: 1210656.1

    From: oracle-l-bounce_at_freelists.org On Behalf Of Niall Litchfield

    The source of the quote was likely the nfs clonedb feature introduced in 11g (maybe R2). Kevin Closson has an intro at http://kevinclosson.wordpress.com/2010/12/23/oracle-database-11g-direct-nfs-clonedb-feature-part-i/ it is a cool feature, but probably won't help Alan.

    Privileged/Confidential Information may be contained in this message or attachments hereto. Please advise immediately if you or your employer do not consent to Internet email for messages of this kind. Opinions, conclusions and other information in this message that do not relate to the official business of this company shall be understood as neither given nor endorsed by it.
  • Amaral, Rui at Jun 28, 2011 at 4:33 pm
    That's what I have seen myself. I have had a number of "opportunities" and haven't seen it work any other way yet.

    Maybe it has to be automagically turned on? Or a hidden feature for 12.x :-P

    From: rajendra.pande_at_ubs.com
    Sent: Tuesday, June 28, 2011 12:17 PM
    To: cicciuxdba_at_gmail.com; oracle-l_at_freelists.org
    Subject: RE: RMAN duplicate only used blocks?

    I don’t believe there is any such feature. Notice the words “I believe� ☺
    What I believe is available in 11G is that RMAN is capable of backing up only used blocks
    But in 1 iTB file if only 200M is used then my understanding will be that somehow magically the output file will still be 1TB even though only 200MB was backed up.
    Of course I have not tested it yet.

    Thanks

    From: oracle-l-bounce_at_freelists.org On Behalf Of Guillermo Alan Bort
    Sent: Tuesday, June 28, 2011 11:51 AM
    To: oracle-l-freelists
    Subject: RMAN duplicate only used blocks?

    So, the situation is this, I have a tablespace with about 600GB of free space (spread out in about 80 datafiles). The entire database itself has about 2TB and we need to copy it to another server. The problem is that we have 1.5TB allocated in the ASM instance in the destination server. We wanted to use RMAN, but the database won't fit. We could use export/import but it would take too long and we don't have anywhere to store the export.

    Someone pointed to me that RMAN was capable of duplicating only the used blocks... I researched a lot but I couldn't find it... so I'm either looking in the wrong place or that someone was wrong. (there is also the possibility that I'm very sleepy).

    I know rman can compress backups and that it only backs up used blocks (when doing a backupset anyway) but I think duplicate just... duplicates... I don't think it resizes and moves stuff around.

    Anyway... I think we will have to go with datapump for this one (we are on 11g anyway), but I was just wondering if I was missing a key feature in rman...

    thanks
    Alan.-

    NOTICE: Confidential message which may be privileged. Unauthorized use/disclosure prohibited. If received in error, please go to www.td.com/legal for instructions.
    AVIS : Message confidentiel dont le contenu peut être privilégié. Utilisation/divulgation interdites sans permission. Si reçu par erreur, prière d'aller au www.td.com/francais/avis_juridique pour des instructions.
  • Guillermo Alan Bort at Jun 28, 2011 at 5:19 pm
    Well,

    This is pretty much what I thought, thanks everyone for your replies :-)

    cheers
    Alan.-
    On Tue, Jun 28, 2011 at 1:33 PM, Amaral, Rui wrote:

    That's what I have seen myself. I have had a number of "opportunities" and
    haven't seen it work any other way yet.

    Maybe it has to be automagically turned on? Or a hidden feature for 12.x
    :-P




    *From*: rajendra.pande_at_ubs.com
    *Sent*: Tuesday, June 28, 2011 12:17 PM
    *To*: cicciuxdba_at_gmail.com; oracle-l_at_freelists.org<
    oracle-l@freelists.org>
    *Subject*: RE: RMAN duplicate only used blocks?


    I don’t believe there is any such feature. Notice the words “I believe”
    J****

    What I believe is available in 11G is that RMAN is capable of backing up
    only used blocks****

    But in 1 iTB file if only 200M is used then my understanding will be that
    somehow magically the output file will still be 1TB even though only 200MB
    was backed up.****

    Of course I have not tested it yet.****

    ** **

    Thanks ****

    ** **
    ------------------------------

    *From:* oracle-l-bounce_at_freelists.org [mailto:
    oracle-l-bounce@freelists.org] *On Behalf Of *Guillermo Alan Bort
    *Sent:* Tuesday, June 28, 2011 11:51 AM
    *To:* oracle-l-freelists
    *Subject:* RMAN duplicate only used blocks?****

    ** **

    So, the situation is this, I have a tablespace with about 600GB of free
    space (spread out in about 80 datafiles). The entire database itself has
    about 2TB and we need to copy it to another server. The problem is that we
    have 1.5TB allocated in the ASM instance in the destination server. We
    wanted to use RMAN, but the database won't fit. We could use export/import
    but it would take too long and we don't have anywhere to store the export.

    Someone pointed to me that RMAN was capable of duplicating only the used
    blocks... I researched a lot but I couldn't find it... so I'm either looking
    in the wrong place or that someone was wrong. (there is also the possibility
    that I'm very sleepy).

    I know rman can compress backups and that it only backs up used blocks
    (when doing a backupset anyway) but I think duplicate just... duplicates...
    I don't think it resizes and moves stuff around.

    Anyway... I think we will have to go with datapump for this one (we are on
    11g anyway), but I was just wondering if I was missing a key feature in
    rman...

    thanks
    Alan.-****


    NOTICE: Confidential message which may be privileged. Unauthorized
    use/disclosure prohibited. If received in error, please go to
    www.td.com/legal for instructions.
    AVIS : Message confidentiel dont le contenu peut être privilégié.
    Utilisation/divulgation interdites sans permission. Si reçu par erreur,
    prière d'aller au www.td.com/francais/avis_juridique pour des
    instructions.
    --
    http://www.freelists.org/webpage/oracle-l

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