1 2 Previous Next 22 Replies Latest reply: Jan 20, 2014 6:24 AM by GTS (DBA) RSS

    Log apply service in 10g dataguard

    GTS (DBA)

      Very Good Morning to all ;

       

      I  have a doubt when applying redo data at standby site. (MAXIMUM PERFORMANCE)

      In physical standby database , 

      I know , Redo Data is applied from  standby redo log (real time apply )  or  archive redo log ( redo apply)

        1) When using max performance mode (physical standby ) ,  which one is default ?

           I do NOT find any answer even googled.

       

           Thanks in advance ..

          

       

        • 1. Re: Log apply service in 10g dataguard
          Baris Yildirim

          Hi

          There is no default. it depends on your requirements.

          Best Regards

          • 2. Re: Log apply service in 10g dataguard
            Baris Yildirim

            Hi

            the most important thing is that redo logs are always shipped from primary to standby

            so you shouldn't worry very much about real time apply.

            A delayed standby is  useful for logical corruption on primary,

            but if failover time is more important for you, you should use real time apply.

            İ prefer to use a delayed standby because log apply time doesn't take long time especially after 11g.

            Best Regards

            • 3. Re: Log apply service in 10g dataguard
              mseberg

              Hello;

               

              It would redo apply since it can be run without SRL. But I would not do it myself.

               

              It is not mandatory to have standby redo log (SRL) files in Maximum Performance mode.

               

              Best Regards

               

              mseberg

              • 4. Re: Log apply service in 10g dataguard
                GTS (DBA)

                Hi Baris ;

                 

                Data Guard supports two redo transport methods using the LNS process (synchronous or asynchronous)

                When using maximum performance mode , ASYNC is default.

                If i enable LogXptMode = 'SYNC' -- > how can i monitor ?

                 

                Any possibilities to check 'whether my db using really sync option ?


                • 5. Re: Log apply service in 10g dataguard
                  Baris Yildirim

                  Hi,

                  I don't think there is a benefit sync in max. performance mode. I think Oracle ignores SYNC in this mode.

                   

                   

                  The V$REDO_DEST_RESP_HISTOGRAM dynamic performance view contains a histogram of response times for each SYNC redo transport destination. The data in

                  this view can be used to assist in the determination of an appropriate value for the LOG_ARCHIVE_DEST_n NET_TIMEOUT attribute.

                   

                  http://docs.oracle.com/cd/E11882_01/server.112/e41134.pdf

                   

                  Also you can use v$dataguard_stats to find out tranport lag. Please use this view on standby.

                   

                  Best Regards

                  • 6. Re: Log apply service in 10g dataguard
                    GTS (DBA)

                    HI mseberg ;

                     

                    What do you say clearly ?  , i am NOT getting from YOU

                     

                    mseberg wrote:

                     

                    It is not mandatory to have standby redo log (SRL) files in Maximum Performance mode.


                    What i assume , " when using maximum performance mode , 

                    No need to create separate standby redo log files at standby site "

                    If standby redo log files not created , then  we can ignore archive destination for standby database also.

                    so ,  real time apply and or redo apply really impossible.

                    I am getting confused from your answer. please clarify

                    • 7. Re: Log apply service in 10g dataguard
                      mseberg

                      Assuming I understand your question.

                       

                      If you are using real time apply then standby redo is mandatory.

                       

                      But if you are in Maximum Performance mode and not using real time apply then standby redo is not mandatory.

                       

                      So what I was trying to say before is the default would be without SRL, since they are not mandatory.

                       

                       

                      Best Regards

                       

                      mseberg

                      • 8. Re: Log apply service in 10g dataguard
                        GTS (DBA)

                        Hi msberg ;

                         

                        Thanks. Information is well. Some thing is very interesting. You have exactly  assumed my question.

                         

                        Consider In  Maximum Performance mode, and not using real time apply then standby redo is not mandatory.

                         

                          1) In this case, should we need to mention archive log destination for standby database ?

                         

                        -------------------------------------------------------

                         

                        What i think . Redo data will reach archive destination via standby redo log files.

                        If stand by redo log files are not there, redo data cannot reach archive destination at standby site also.

                            Here , Redo apply also not possible.  Because redo apply is applied only from archived redo logs.

                          2) How data guard is managing here ?     

                         

                            Please provide links to explain this things ?  -- I am having many questions here.

                            I cannot ask all question to you. please don't mind . 


                            Thanks once again !

                            

                                

                        • 9. Re: Log apply service in 10g dataguard
                          mseberg

                          Not sure I have a link. Almost 100 percent sure I read it this book:

                           

                          http://www.visi.com/~mseberg/data_guard/new_dg_book.html

                           

                          Emre Baransel and Nassyam Basha are execellent sources of information. Here are their sites:

                           

                          http://emrebaransel.blogspot.com/

                          http://www.oracle-ckpt.com

                           

                          Best Regards

                           

                          mseberg

                          • 10. Re: Log apply service in 10g dataguard
                            GTS (DBA)

                            Hi Baris ;


                            When using maximum performance mode , If i enable LogXptMode = 'SYNC'

                            Any possibilities to check 'whether my db using really sync option ?

                            BarisYildirim wrote:

                             

                            Hi,

                            I don't think there is a benefit sync in max. performance mode. I think Oracle ignores SYNC in this mode.

                            Yes baris, i think so.  but i have some collections.


                            If possible , could you please check once again ??

                             

                            Requirements for maximum performance mode

                             

                            Redo archival process

                            Lgwr or Arch

                            Network transmission mode

                            ASYNC  if using LGWR , SYNC if using ARCH

                            Disk write option

                            Noaffirm

                            Standby redo logs?

                            No, but  recommended.

                            Standby database type

                            Physical or logical

                             

                            Above information given by my trainers  ...

                            • 11. Re: Log apply service in 10g dataguard
                              GTS (DBA)

                              Hi msberg

                               

                              I got soft copy from here . Thanks for the link. 

                              I 'll  try to  do it.

                              • 12. Re: Log apply service in 10g dataguard
                                Baris Yildirim

                                Hi

                                In maximum performance mode, if you use LGWR process to ship redo data, async is used, but if you use ARCH, sync is used.

                                I recommend you to use LGWR-ASYNC mode instead of ARCH-SYNC mode because if you use ARCH process, you will lose all transactions in current redo log file on your primary in a failover.

                                 

                                Best Regards

                                • 13. Re: Log apply service in 10g dataguard
                                  GTS (DBA)

                                  Thanks baris ;

                                   

                                  BarisYildirim wrote:

                                   

                                  Hi

                                  In maximum performance mode, if you use LGWR process to ship redo data, async is used, but if you use ARCH, sync is used.

                                  I recommend you to use LGWR-ASYNC mode instead of ARCH-SYNC mode because


                                  if you use ARCH process, you will lose all transactions in current redo log file on your primary in a failover.

                                   

                                  Best Regards

                                   

                                  I assume  if i  use arcn proces , 

                                  Consider , i am planning  to do failover ,

                                  In current standby database redo log files will lose entire data ? ( before going to act as primary ) ?

                                   

                                  --------------

                                   

                                  When doing failover , current redo log flle data  will be moved to standby archive destination .

                                  If so ,  i think no possibilities to loose  data - am i right ?

                                  • 14. Re: Log apply service in 10g dataguard
                                    Baris Yildirim

                                    Yes that's right when you use arch process

                                    I assume  if i  use arcn proces ,

                                    Consider , i am planning  to do failover ,

                                    In current standby database redo log files will lose entire data ? ( before going to act as primary ) ?

                                     

                                    Sorry but No.... because a failover means that you have lost your primary so it's impossible current redo log file data to ship to standby archive destination. it's true when you use arch process so I recommended you to use lgwr async. A failover is done on standby to convert it primary.

                                     

                                    When doing failover , current redo log flle data  will be moved to standby archive destination .

                                    If so ,  i think no possibilities to loose  data - am i right ?

                                     

                                    Best Regards

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