7 Replies Latest reply on Aug 27, 2018 3:44 PM by ANNEC

    duplicate from active database

    ANNEC

      I am using oracle 12c on windows.

       

      A question about the duplicate from active database.

      As I understand duplicate from active database is not using pre existing backup sets.

      But I see duplicate from active database has two methods,  one is push-based the other is pull-based.

      The push based is to copy data files and log files from target to duplicate database, using more resource on target database server.

       

      For pull based it uses:

      duplicate .. from active database using backupset...

       

      So what is the backupset?  There is no backupset...

      Does it mean it will first do a backup first ?

       

      Thanks

        • 1. Re: duplicate from active database
          CristianR-Oracle

          If you have access to MOS see note below:

          RMAN ACTIVE DUPLICATE USING BACKUPSET IN 12C(NEW FEATURE) (Doc ID 1987193.1)

           

          or link below:

          https://docs.oracle.com/database/121/BRADV/rcmdupdb.htm#BRADV010

           

          Long story short - RMAN will backup the source database and transfer the backups accross the network instead of whole database as image copies.

          • 2. Re: duplicate from active database
            ANNEC

            Thanks. I have read the documents.

             

            What confused me is the below two paragraph of statements:

             

            1. RMAN then manages the copying of the database to the auxiliary instance over the network. No backups of the source database are required.

            2. When RMAN performs active database duplication using backup sets, a connection is established with the source database and the auxiliary database. The auxiliary database then connects to the source database through Oracle Net Services and retrieves the required database files from the source database. This method of active database duplication is also to as the pull-based method.

             

            One said no backupset required. The other said using backup sets.

            And in the second paragraph it does not say anywhere it will do a backup.

             

             

             

             

            • 3. Re: duplicate from active database
              Dude!

              You're reading about the two methods 12c provides with active duplication. Perhaps you are confusing backup-based duplication with 12c active duplication using backup sets.

               

              I agree however that the Oracle documentation regarding the matter is somewhat ambiguous or confusing. Sometimes it helps to create a test environment and practice. The below is what I understand:

               

              In 11g, backup-based duplication uses pre-existing RMAN backup sets or RMAN image copies of database files to duplicate the database. This allows you to duplicate a database with or without a connection to the target, depending on whether or not you have a RMAN catalog database. Active duplication in 11g copies the target database files to the auxiliary instance internally using SQL*NET. It creates image copies of the target database files, but does not use RMAN backup sets or RMAN image copies.

               

              Active duplication in 12c can now be done using a push or pull method:

               

              Push method: It relies on SQL*NET to internally transmit image copies of the database files to the auxiliary instance. This is the same as in 11g.

               

              Pull method: The target database creates a RMAN backup and uses SQL*NET to transmits the backup sets to the auxiliary location. The restore of the database to duplicate the target database is done at the auxiliary instance. To use the pull method, you specify the new "using backupset, or section size" clause. Note however, that under certain circumstances, as described in the documentation, active duplication will default to using the pull method.

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              • 4. Re: duplicate from active database
                CristianR-Oracle

                "No backups of the source database are required." - you don't need to have a backup - RMAN will take on on the fly during duplicate.

                 

                Best to test to see what is happenig.

                • 5. Re: duplicate from active database
                  Dude!

                  Good examples that clearly explain and demonstrate 12c active duplication using backup sets are difficult to find. So far I couldn't find precise information that outlines how RMAN creates these backup sets, or whether it uses existing backups. Again it is important to distinguish between RMAN backup-based and active duplication and not to confuse both methods.

                   

                  I would not mind to know myself, so I decided to test it. The console of RMAN active duplication using backup sets shows "using network backup set from service CDB1", for example. From what I understand, online image copies or backup sets during active duplication are directly transmitted via Oracle Net - they are not written as backups or image copies to disk.

                   

                  Oracle 12c Active Database Duplication Using Backup Sets Example

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                  • 6. Re: duplicate from active database
                    Dude!

                    CristianR-Oracle wrote:

                     

                    "No backups of the source database are required." - you don't need to have a backup - RMAN will take on on the fly during duplicate.

                     

                    Best to test to see what is happenig.

                     

                    Not required is quite ambiguous. From what I've seen so far, active duplication does not seem to make use of any existing RMAN backup. It doesn't even display information about creating a backup - it's just restoring from a "net backup". My best guess is that duplicate uses RMAN backup and image copy technology, but instead of creating files, it streams the output through Oracle Net. RMAN on the auxiliary instance uses the data stream directly to restore the database files.

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                    • 7. Re: duplicate from active database
                      ANNEC

                      Thanks so much. I think the document is ambiguous about this, and hard to understand or to learn.

                      I have the same experience, I looked for in every place of the document and also the log for the duplicate from active database (pull method), I don't see any place that does a backup.

                       

                      But your explanation make senses to me.  Thanks !