9 Replies Latest reply: Jul 20, 2014 6:48 PM by Kent D Sorber RSS

    Control File or Catalog schema ?

    james_p

      DB Version: 11.2.0.4

      Platform: RHEL 6.3

       

      This week we are moving all our RMAN DBs' backups out of tape to DataDomain Disk based backup. Today we came to know that , we won't be using catalog schema for storing RMAN backup repository. Instead each DB's Control file will be its repository.

       

      Is using Control File as the catalog a good idea ?

       

      For example , a cloning/Duplicate scenario mentioned in the below post where a DB is being duplicated in the same machine can become difficult if you are not using RMAN catalog schema. Right ?

       

      https://community.oracle.com/thread/3584083

        • 1. Re: Control File or Catalog schema ?
          asifkabirdba

          If you don't use RMAN catalog then there will  be no issue.  Control file will take care of all the metadata of RMAN backup.  Enable controlfile autobackup on for all the DB server of your environment. Also, take care the parameters CONTROLFILE_RECORD_KEEP_TIME parameter value as per your requirement.

           

           

          Use RMAN duplication for the same server. Hope there won't be any difficulties.

           

           

          Regards

          Asif Kabir

          • 2. Re: Control File or Catalog schema ?
            EdStevens

            You can do what you want without a catalog, but having a catalog certainly gives you more options and makes life easier.  Why would you not use a catalog?

            • 3. Re: Control File or Catalog schema ?
              Nip-Oracle

              Certainly not a a good idea, if your control file is lost !  This way, all backup information will be lost as well, and its' really painful to restore/recover in that situation.

              • 4. Re: Control File or Catalog schema ?
                james_p

                Yes. But, control file can be restored from backup.

                 

                EMC sent this DataDomain implementor guy here. He is not a DBA , but an RMAN expert with some knowledge of Oracle RDBMS.

                He insists on using control file as the catalog rather than a Catalog schema. He wants me to point out one Restore or Backup scenario which schema based catalog can do and Control file based catalog cannot or have difficulty with.

                • 5. Re: Control File or Catalog schema ?
                  Nip-Oracle

                  Ok, the scenario is :

                   

                  You lost / deleted / corrupted the control file itself !

                   

                  In this case, unless you don't know the exact Control file Backup piece handles (via preserved backup logs, etc..),  you can not restore the contol file.

                   

                  And unless the control file is restored, we can not have backup information for rest of the db, e.g. database files, archived logs, etc.

                   

                   

                  Hence, if not using catalog schema,  make sure you have a way to  identify the control file backup piece handles.

                  • 6. Re: Control File or Catalog schema ?
                    yoonas

                    Once you introduce RMAN catalog database you have one more database to manage

                    https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1276847400346367990

                    • 7. Re: Control File or Catalog schema ?
                      EdStevens

                      yoonas wrote:

                       

                      Once you introduce RMAN catalog database you have one more database to manage

                      https://asktom.oracle.com/pls/asktom/f?p=100:11:0::::P11_QUESTION_ID:1276847400346367990

                      And your point is ....?

                       

                      I can't remember the last time I had to do anything to "manage" my catalog database.

                      • 8. Re: Control File or Catalog schema ?
                        Phill W.

                        As I understand it:

                        The Control File is always used to hold Backup (and other) metadata.

                        The Recovery Catalog is an additional store for the same metadata.

                         

                        The difference is that if you only have the Control File (of course you mean "Files", but we'll let that slide for now) and you restore your database, then your Control File gets overwritten in the process, along with all the metadata that was in it. 

                         

                        So if, for example, you'd done a Tablespace Point-in-Time Recovery (TSPITR) and you found that you needed to have another go at restoring it ...

                        "Oops, can we bring it back to just six hours ago?  We don't think 'X' was the problem."

                        ... then you can't (easily).  With a Recovery Catalog, you can; you can have as many goes at doing the TSPITR as you might need.

                         

                        Regards,

                           Phill  W.

                        • 9. Re: Control File or Catalog schema ?
                          Kent D Sorber

                          Hi-

                           

                          The recovery catalog preserves RMAN repository information if the control files are lost making it easier to restore and recover after the loss of the control files.

                          Also your backup control file may not contain complete information about current available backups which may not allow you to restore your database to a consistent state causing loss of work and data.

                          The recovery catalog stores much more extensive history of your backups than the control files which has limits on the number of control file records and your control files can also become large.

                          Managing a recovery catalog is simple and it can be used for all your Oracle database backups.

                           

                          Regards, 

                          Kent D Sorber OCP