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6 Replies Latest reply: Oct 11, 2012 5:24 PM by onedbguru RSS

mulitiple scan IP

lm*422407*sh Newbie
Currently Being Moderated
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) Guru
    Currently Being Moderated
    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
    KuljeetPalSingh Guru
    Currently Being Moderated
    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 Pro
    Currently Being Moderated
    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 Newbie
    Currently Being Moderated
    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 Newbie
    Currently Being Moderated
    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 Pro
    Currently Being Moderated
    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.

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