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Oracle 11g Release 2 – SCAN explained

Starting with Oracle 11g Release 2 Oracle introduced a new cluster database connection concept: SCAN – “Single Client Access Name”.

SCAN on the server side

When installing a 11g Release 2 grid infrastructure you are asked for the cluster name which will be part of the SCAN. The notation for the SCAN is:


For instance if your cluster is named “rac” and the domain “regner.de” the SCAN name will be “rac-scan.regner.de”.

In order to successful install grid infrastructure you need to configure your DNS (hosts file entries will not work!) prior installing grid infrastructure to resolve the name accordingly. Oracle requires at least one, better three IPs configured for the scan name. Your DNS zone file might look like this:



In the example zone file above we configured three IPs for the scan:, and

After installation you will find three listener processes running (separated on all cluster nodes) as shown in the following figure:


Listener for SCAN2 and SCAN3 are running on node “rac1″ and listener for SCAN1 is running on node “rac2″. For each SCAN listener there will be a dedicated network interface running with the same IP as configured in DNS:


Client connections

Connection to database “RAC11P” using SCAN would use this tnsnames entry:

RAC11P =

The ”old fashioned” way still works:

RAC11P_old =

Connecting to a named instance:

RAC11P =
Categories: Oracle 11g Release 2 Tags:
  1. Sayantan
    December 18th, 2009 at 08:16 | #1


    how to configure the scan?? is just those tns/listiners.ora entry(s) enough?


  2. Ronny Egner
    December 19th, 2009 at 11:06 | #2

    Yes, the shown TNSNAMES.ORA is enough.

  3. Sayantan
    February 18th, 2010 at 14:45 | #3

    @Ronny Egner

    whats those bond for?

  4. Ronny Egner
    February 18th, 2010 at 17:08 | #4

    I dont know “bond” you are referring to. Basically a network bond provides high availability and/or increased throughput.

  5. Sayantan
    February 24th, 2010 at 18:07 | #5

    @Ronny Egner

    i was reffering to the bond0 etc. in ifconfig otput….


  6. Ronny Egner
    February 26th, 2010 at 23:31 | #6

    bond0 is the name of the network interface. “bond” means network interfaces are bonded in any way….

  7. sayantan
    April 11th, 2010 at 10:51 | #7

    how to create network bond???

  8. Ronny Egner
    April 13th, 2010 at 14:28 | #8

    See this link here and look for “Configure Network Bonding”

  1. October 15th, 2009 at 10:41 | #1