Oleksandr Denysenko's Blog

24.09.2009

RAC: Correct DISPATCHERS configuration (no more ORA-12545)

Filed under: RAC — odenysenko @ 10:09
Tags: , ,

I have seen a lot information about correct configurations of Oracle Real Application Cluster’s environment to provided Server Side Load Balancing with good information. But most of it relates to dedicated server configurations. What about shared server configurations ?

The main problem is one like with dedicated server configuration – if we don’t specify HOST of the dispatcher then PMON will take result of locally executed command hostname, which is in most cases public node name, and bind dispatcher’s listening end-points on it – which IS WRONG!

So we have to provide VIP nodename/address for dispatchers like this:

DISPATCHERS="(ADDRESS=(PROTOCOL=TCP)(HOST=node1-vip))"

We have to provide different values for DISPATCHERS parameter for each instance:

ALTER SYSTEM SET DISPATCHERS="(ADDRESS=(PROTOCOL=TCP)(HOST=node1-vip))" SID='INST1';
ALTER SYSTEM SET DISPATCHERS="(ADDRESS=(PROTOCOL=TCP)(HOST=node2-vip))" SID='INST2';

And DO NOT specify LISTENER parameter for DISPATCHERS!

PMON will register dispatcher’s listening end-points with listeners specified in REMOTE_LISTENER parameter – which also works for dedicated server configuration.

Have a nice RACcing!

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2 Comments »

  1. Useful. Thanks.
    Could you please explain what happens in the scenario when VIP fails over to another node and then comes back to the original node?

    Comment by Antony — 17.11.2010 @ 18:26 | Reply

  2. Hi Antony!

    VIP fails back to original node, then listener will be started using address of this VIP, then after some time PMON will register all services with this listener and users will be able to connect to them.

    You man speed up process of registering services with listeners by issuing:
    ALTER SYSTEM REGISTER;

    Bye.
    Oleksandr

    Comment by odenysenko — 17.11.2010 @ 21:19 | Reply


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