11 Replies Latest reply on Apr 21, 2020 3:24 AM by Beauty_and_dBest

    Dataguard Setup

    Beauty_and_dBest

      11g

      OL6

       

       

      Hi ALL,

       

      We have active dataguard setup  using > ALTER DATABASE RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT FROM SESSION;

      I understand the above command is the only distinction between active not none-active dataguard right?

       

      I tried to create an table on primary database, and in split second the table is also created at the standby database.

      This happened even if there is no logfile switch and the archve log in not yet in transport.

       

      My Question is .....Does this mean that, when real life disaster and database failure happens,  I do not have data loss even if logs are not transported?

       

       

      Please help understand the dataguard process.

       

       

      Kind regards,

      jc

        • 1. Re: Dataguard Setup
          JohnWatson2

          Your understanding of Data Guard and Active Data Guard is wrong. All forms of Data Guard rely on transporting and applying redo, archived or not. Active Guard means opening the standby database.

          I know you have an aversion to reading, how about watching some videos? For example:

          https://skillbuilders.com/course/oracle-data-guard-in-ten-minutes/

          https://skillbuilders.com/course/how-to-create-an-oracle-physical-standby-database-a-data-guard-tutorial/

          1 person found this helpful
          • 2. Re: Dataguard Setup
            Beauty_and_dBest

            Thanks John

            • 3. Re: Dataguard Setup
              Joerg.Sobottka

              Depending on your DG setup the logwriter or archive logwriter does ship anything to the standby at the time it happens on primary. In addition, you can setup the standby to have a time lag for shipping and/or applying things that are shipped to the standby. With this additional feature, you can, e.g. use the standby to catch logical errors (like dropping data) from primary (until the lag is over, then you still have to restore/recover or flashback the primary). There is no difference between Data Guard and Active Data Guard for this behaviour.

               

              In addition, the Active Data Guard allows to use the standby:

              - for reporting (and with 19c a little DML also) while open it (read-only), without ADG you have to stay in MOUNT status with the standby DB

              - with some additional cool things like automatic block repair, etc.

              ADG is an extra cost option to the Enterprise Edition while Data Guard is included in EE.

              1 person found this helpful
              • 4. Re: Dataguard Setup
                Beauty_and_dBest

                Thanks Joerg and ALL,

                 

                So we pay expensive active dataguard LICENSE by using this command only?

                 

                startup mount;

                ALTER DATABASE OPEN READ ONLY;

                 

                If we do not open it read only, there is no need to pay much?

                 

                Please clarify...

                 

                 

                Regards,

                • 5. Re: Dataguard Setup
                  Mike Navickas

                  One additional feature of Active Data Guard - ability to offload database backups  to standby database (backups made against standby database versus primary) and create a block change tracking file on standby. I seen some customers using ADG option just for this purpose to backup big database.

                  However majority of ADG option users are using it for ability to offload some reporting(read-only) load to a standby database that also could be used for enhanced availability (DR fail-over)

                  1 person found this helpful
                  • 6. Re: Dataguard Setup
                    BPeaslandDBA
                    One additional feature of Active Data Guard - ability to offload database backups  to standby database

                     

                    Just make sure such backups meet your recovery requirements. http://www.peasland.net/2012/05/14/recovery-requirements-before-backups/

                     

                    It sounds like a great idea to offload your backups to a system that isn't being used that much until one day you need to restore the primary db from that backup and you realize you now have to transfer that backup (over the wire or sneaker net) back to the primary data center before you can begin the restore.

                     

                    Cheers,
                    Brian

                    1 person found this helpful
                    • 7. Re: Dataguard Setup
                      Beauty_and_dBest

                      Thanks Brian and mnav,

                       

                      I can not understand the purpose of offloading backups

                      Why making lots of backup when you have already RMAN backups.

                      I do RMAN backups on both Primary and Standby, this way I can purge archivelogs after a successful backup.

                      So logically/physically I have now 3 backups of our Primary database.

                       

                       

                      Kind regards,

                      • 8. Re: Dataguard Setup
                        BPeaslandDBA

                        I can not understand the purpose of offloading backups

                         

                         

                        The whole idea is that taking a backup of your database can be resource intensive, specifically I/O resources. Some DBAs like the idea of shifting that I/O demand to a system that has an exact duplicate of the database but isn't really being used, i.e. the standby database. They reason that end users won't get negatively impacted by the resource demands of the backup process. Nice idea, but...as I pointed out, sucks when you realize you need that backup at the primary site, not the standby site.

                         

                        I do RMAN backups on both Primary and Standby, this way I can purge archivelogs after a successful backup.

                        So logically/physically I have now 3 backups of our Primary database.

                         

                        I always like to have options when it comes to restoring databases and getting data back and available again. So I wouldn't balk at that number of backups. In fact, it matches my situation. I take backups of the primary database at the primary site. I also have a physical standby database at the DR site. I do take backups of the standby as well, but that is because we clone those backups to make non-production databases, i.e. dev and test databases. But we can use those backups for recovery of the standby if we need to.

                         

                        Cheers,
                        Brian

                        1 person found this helpful
                        • 9. Re: Dataguard Setup
                          Beauty_and_dBest

                          Thanks Brian,  for the clear explanation. 

                           

                          I understand you have blog site?

                          Can you give me link of your blog with topic, or make a blog on how to create a  standby database  for a RAC database?

                          Is it possible to create an "ordinary" single-node non-rac standby database  for a RAC database?

                           

                           

                          Please help...

                           

                          Kind regards,

                          • 10. Re: Dataguard Setup
                            BPeaslandDBA

                            I understand you have blog site?

                            Can you give me link of your blog with topic,

                             

                            My personal blog is at http://www.peasland.net/

                             

                            or make a blog on how to create a standby database for a RAC database?

                             

                            I wrote instructions for the IDGOUG - (International Data Guard Oracle User Group) on how to do this. First, I create a single-instance physical standby with this:

                            How to Create a Physical Standby Database then I convert that to Oracle RAC: How to Create a RAC Standby Database

                             

                            Is it possible to create an "ordinary" single-node non-rac standby database for a RAC database?

                             

                            Yes, it is possible. Oracle standby databases let you mix and match. You can have both primary and standby be single-instance or both be RAC. You can have a RAC primary and a single-instance standby. You can have a single-instance primary and a RAC standby, but that would be rare. And if you are using RAC, you can have any number of nodes in the primary and that can be different than the number of nodes in the standby. Basically, there are no rules when it comes to RAC and the primary and standby relationship. As I said, you can mix and match to suit your needs. At the end of the data, you still have redo transport and redo apply. You can set up redo transport no matter if the primary is one, two, or three nodes or more. Redo transport doesn't care if you are using RAC or not. That redo is received on the standby. Just make sure if you are using RAC on the standby that your redo transport is sent to the SCAN Listeners, not a regular listener. Redo apply doesn't care how many nodes are in the standby. It used to be if you have a RAC standby, then only one node did the redo apply. However, I think it was 12.2 that allowed multiple nodes to apply redo.

                             

                             

                            Cheers,
                            Brian

                            1 person found this helpful
                            • 11. Re: Dataguard Setup
                              Beauty_and_dBest

                              Thanks Brian!