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

        Hi baris ;

         

        I am in confusion.  Now i  am leaving. Tomorrow we 'll  continue ..

        Thanks a lot.

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

          Hi

           

          see you tomorrow.

           

          have a nice day my firend.

           

          Regards

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

            Hi  Bris ;

             

            I want to clear  now.

             

            my primary db : orcl

            standby db : clone

            When trying to to failover i.e.  clone db will be changed as primary.

            However we lost all information in orcl db (so ,  no information 'll reach current standby archive log destination). - This is ok.

            if so , when using LGWR ASYNC -  can we save anything ?


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

             

            Please explain little more clearly !!

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

              Hi

               

              I am glad to hear that my friend.

               

              it's Ok Your're right

              my primary db : orcl

              standby db : clone

              When trying to to failover i.e.  clone db will be changed as primary.

              However we lost all information in orcl db (so ,  no information 'll reach current standby archive log destination). - This is ok.

               

              if you use LGWR ASYNC mode you can recover transactions which are in Primary's current redo log file. Furthermore you are in ASYNC mode so maybe you can lose some transactions in primary's current redolog file.

               

              What size is your redo log group in your pirmary.

               

              select * from v$dataguard_stats --> run this on stanbdy and post me the result

               

              Please look up this link

               

              For ARCH SYNC, look Figure 5-3

               

              For LGWR SYNC, look Figure 5-4

               

              For LGWR ASYNC, look Figure 5-5

               

              and read explains above each figure

               

              http://docs.oracle.com/cd/B19306_01/server.102/b14239/log_transport.htm

               

              Best Regards

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

                Hi baris ;


                BarisYildirim wrote:

                 

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

                 

                Best Regards


                What i think ,

                when current redo log gets full then it switch to to next redo then archive is generated and 

                send to standby. In primary ,

                if current redo is gets croupt  when your transaction is stored and  if it is not send to standby.


                Anyhow  if we use ( LGWR OR ARCH ), lost is lost

                - How you  can recover the  data when using lgwr instead of arch  ?

                If current redo got croupt so your all transaction will be lost ...

                only one thing can save if we have  multiplex of redo members.


                My question is

                why do you recommend  particularly  LGWR  when trying to do failover ?



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

                  Hi my friend,

                   

                  Let's look up

                   

                  For LGWR ASYNC

                   

                  When the LGWR and ASYNC attributes are specified, the log writer process writes to the local online redo log file, while the network server (LNSn) processes (one for each destination) asynchronously transmit the redo to remote destinations. The LGWR process continues processing the next request without waiting for the LNS network I/O to complete.

                   

                  now please look at this figure 5-5 on the below link

                   

                  http://docs.oracle.com/cd/B19306_01/server.102/b14239/log_transport.htm#i1148216

                   

                  For ARCH SYNC

                   

                  On the primary database, after the ARC0 process successfully archives the local online redo log to the local destination (LOG_ARCHIVE_DEST_1), the ARC1 process transmits redo from the local archived redo log files (instead of the online redo log files) to the remote standby destination (LOG_ARCHIVE_DEST_2).

                   

                  now please look at this figure 5-3 on the below link

                   

                  http://docs.oracle.com/cd/B19306_01/server.102/b14239/log_transport.htm#i1148216

                   

                  so as you see if you use LGWR ASYNC, you may lose last a few transactions, but ARCH SYNC you lose all transations in current redo log file.

                   

                  Regards

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

                    Hi baris ;

                     

                    Thanks.

                     

                    Many things are confusing from  previous answer.

                    I think you are strongly saying  always try to use ' LGWR ASYNC'  ..

                     

                    From your previous reply , diagram is showing some thing different.

                    we have to continue. I'll be back.

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

                      Hi

                      You're welcome.

                      Yes I recommend you to use lgwr async when you use maximum performance mode

                      Best Regards

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