6 Replies Latest reply: Oct 11, 2012 7:24 PM by onedbguru RSS

    mulitiple scan IP

    lm*422407*sh
      Can i use mulitiple scan IP in TNS name like we use for VIP

      text.test.com = (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = dg654-vip.autodesk.com)(PORT = 1521))
      (ADDRESS = (PROTOCOL = TCP)(HOST = dg656-vip.autodesk.com)(PORT = 1521))
      (LOAD_BALANCE = off)(CONNECT_DATA =(SERVER = DEDICATED)
      (SERVICE_NAME = text.test.com)
      (FAILOVER_MODE =(TYPE = SELECT)(METHOD = BASIC)
      (RETRIES = 180)(DELAY = 5))))
        • 1. Re: mulitiple scan IP
          Sebastian Solbach -Dba Community-Oracle
          Hi,

          the answer depends, since your intentions are not quite/your question is a bit vague:

          => If you ask if you can enter the SCAN IP addresses, instead of the SCAN name, you can do that
          (Pre 11.2 clients need all 3 SCAN IPs addresses in the connect string (tnsnames.ora) to use all SCAN IP adresses, since a 10g client cannot resolve the SCAN to 3 IP addresses):

          (DESCRIPTION =
          (ADDRESS = (PROTOCOL = TCP)(HOST = 10.10.10.1)(PORT = 1521))
          (ADDRESS = (PROTOCOL = TCP)(HOST = 10.10.10.2)(PORT = 1521))
          (ADDRESS = (PROTOCOL = TCP)(HOST = 10.10.10.3)(PORT = 1521))
          (LOAD_BALANCE = off)
          (CONNECT_DATA =(SERVER = DEDICATED)
          (SERVICE_NAME = text.test.com)
          (FAILOVER_MODE =(TYPE = SELECT)(METHOD = BASIC)
          (RETRIES = 180)(DELAY = 5))))

          (However I would set LOAD_BALANCE to true when using SCAN).

          => If you asked if in a DG environment you can reference multiple SCAN addresses, this is also possible:
          See
          http://www.oracle.com/technetwork/database/features/availability/maa-wp-11gr2-client-failover-173305.pdf

          => However if your question was, if you can have multiple SCAN names for the same DB or if you can have the same SCAN multiple times in the address list, then no (it does not work, makes no sense, nor does it work as you would expect).

          Regards
          Sebastian
          • 2. Re: mulitiple scan IP
            415289
            lm**** wrote:
            Can i use mulitiple scan IP in TNS name like we use for VIP

            text.test.com = (DESCRIPTION =
            (ADDRESS = (PROTOCOL = TCP)(HOST = dg654-vip.autodesk.com)(PORT = 1521))
            (ADDRESS = (PROTOCOL = TCP)(HOST = dg656-vip.autodesk.com)(PORT = 1521))
            (LOAD_BALANCE = off)(CONNECT_DATA =(SERVER = DEDICATED)
            (SERVICE_NAME = text.test.com)
            (FAILOVER_MODE =(TYPE = SELECT)(METHOD = BASIC)
            (RETRIES = 180)(DELAY = 5))))
            short answer- yes ,you can but specify the scan name to take actual advantage of this feature.
            • 3. Re: mulitiple scan IP
              onedbguru
              Your understanding of SCAN seems to be severely lacking. http://www.lmgtfy.com/?q=oracle+scan+pdf Read it.

              SCAN is multiple IPaddresses that are selected in a round-robin fashion. Putting more than one SCAN address in your connection defeats the purpose of SCAN (Single Client Access Name) altogether.
              • 4. Re: mulitiple scan IP
                967650
                Hi,

                Yes inspight of mentioning three SCAN IPs we can mention SCAN name ( as mentioned in /etc/hosts ) in tnsnames.ora and with LOAD_BALANCE off we can attain load balancing which will provide pure use of Scan.

                Thanks
                • 5. Re: mulitiple scan IP
                  TRLange
                  The originator of this thread never mentioned what release of Oracle Client they are using to connect to the database.

                  I believe that Sebastian makes a valid point here when he says "(Pre 11.2 clients need all 3 SCAN IPs addresses in the connect string (tnsnames.ora) to use all SCAN IP adresses, since a 10g client cannot resolve the SCAN to 3 IP addresses)".

                  I use the same three SCAN IP address setup in my TNSNAMES.ORA entry, because I'm using a 10.2 client. So, onedbguru, is my SCAN understanding severely lacking as well? I would always want to understand the environment before criticizing.
                  • 6. Re: mulitiple scan IP
                    onedbguru
                    TRLange wrote:
                    The originator of this thread never mentioned what release of Oracle Client they are using to connect to the database.

                    I believe that Sebastian makes a valid point here when he says "(Pre 11.2 clients need all 3 SCAN IPs addresses in the connect string (tnsnames.ora) to use all SCAN IP adresses, since a 10g client cannot resolve the SCAN to 3 IP addresses)".
                    The only issue I have seen in extensive testing, is that the 10g WILL use the first IP address returned from DNS. If that SCAN address is down, it may abort/error, however, if there is a retry, it will attempt to resolve the address again and would successfully connect to a surviving node. I have seen a application using the SCAN name only in 10g client successfully for more than a year now. While the docs (SCAN.pdf) say one thing, the reality is that it
                    will work in most situations.

                    So, the real problem is with the application and their inability to stay current. Bottom line, if you upgrade the database, it is also time to upgrade the client. More often than not, you can generally upgrade the client without the application even knowing you did it.
                    I use the same three SCAN IP address setup in my TNSNAMES.ORA entry, because I'm using a 10.2 client. So, onedbguru, is my SCAN understanding severely lacking as well? I would always want to understand the environment before criticizing.