Re: Configuring a client TNS entry for TAF

Will,

Using only client-side failover is not sufficient for what you are trying to do. As Andrea mentioned, there are server-side services configurations that have to be done as well. The Oracle MAA group puts out a really good white paper on this.
https://www.oracle.com/technetwork/database/availability/client-failover-2280805.pdf

On Mon, Sep 24, 2018 at 5:33 PM Andrea Monti <ilsuonogiallo_at_gmail.com> wrote:

> Hi Will
>
> If you want to use connect-time failover you should configure a custom
> service_name and a tns entry like
>
> CONNECT_TIME_FAILOVER =
> (DESCRIPTION =
> (ADDRESS_LIST =
> (FAILOVER=on)
> (LOAD_BALANCE=on) #optional - only use this to process different
> addresses from first to last
> (ADDRESS = (PROTOCOL = TCP)(HOST = primHost)(PORT = 1521))
> (ADDRESS = (PROTOCOL = TCP)(HOST = stbyHost)(PORT = 1521))
> )
> (CONNECT_DATA =
> (SERVICE_NAME=CUSTOM_SERVICE_NAME)
> (failover_mode =
> (RETRIES = 180)
> (DELAY = 5)
> )
> )
> )
>
> This will work, as lons as the service CUSTOM_SERVICE_NAME will only be
> active on the PRIMARY database.
>
> If you want to use TAF you should use Oracle RAC rather than Oracle Data
> Guard. TAF will protect your sessions from instance crash; additionally,
> TAF may protect your select and your transactions, too (check how to use
> FAILOVER_METHOD!).
> However, TAF will not protect you from database failures:Data Guard and
> site switchover will protect you in case of a database failure, but they
> will not protect your ongoing select and transactions, as long as I know.
>
> regards
>
> Andrea
>
>
> Il giorno lun 24 set 2018 alle ore 23:07 Will Beldman <wbeldma_at_uwo.ca> ha
> scritto:
>
>> I have two databases configured under Data Guard:
>> * PRIM - Usually the primary
>> * STBY - Usually the standby
>>
>> From what I read, the following configuration should work:
>> ===============
>> PRIM =
>> (DESCRIPTION =
>> (ADDRESS_LIST =
>> (ADDRESS = (PROTOCOL = TCP)(HOST = primHost)(PORT = 1521))
>> )
>> (CONNECT_DATA =
>> (SERVICE_NAME = PRIM)
>> (FAILOVER_MODE = (BACKUP =
>> STBY)(METHOD=basic)(TYPE=select)(RETRIES=10)
>> (DELAY=10))
>> )
>> )
>>
>> STBY =
>> (DESCRIPTION=
>> (ADDRESS_LIST=
>> (ADDRESS=(PROTOCOL=TCP)(HOST=stbyHost)(PORT=1521))
>> )
>> (CONNECT_DATA=(SERVICE_NAME=STBY))
>> )
>> ===============
>>
>> I can successfully switch over the database.
>>
>> My intent is for the client to *attempt* to connect to PRIM, but if that
>> fails, the connection passes through to STBY instead.
>>
>> (Since PRIM is now a standby but still listening for connections, to
>> ensure
>> failure on PRIM, I completely shut off the database. More on this later)
>>
>> As expected, my connection to STBY is perfect:
>> ===============
>> sqlplus system/******_at_STBY
>>
>> ...
>>
>> SQL>select DATABASE_ROLE from v$database;
>>
>> DATABASE_ROLE
>> ----------------
>> PRIMARY
>> ===============
>>
>> However, as *not* expected, my connection to PRIM fails immediately:
>> ===============
>> sqlplus system/******_at_PRIM
>>
>> SQL*Plus: Release 12.1.0.2.0 Production on Mon Sep 24 16:52:52 2018
>>
>> Copyright (c) 1982, 2014, Oracle. All rights reserved.
>>
>> ERROR:
>> ORA-12514: TNS:listener does not currently know of service requested in
>> connect
>> descriptor
>> ===============
>> It looks like RETRIES and DELAY is not respected here as the failure is
>> immediate.
>>
>> So a few questions:
>> 1. As is, what am I not understanding? Why isn't my configuration doing
>> anything I expect it to?
>> 2. Obviously I have another issue where PRIM is in a MOUNT status and
>> "accepting" connections. So my connections to PRIM produced ORA-01033.
>> What is
>> the preferred way to configure TAF with Data Guard in a RAC environment?
>> I
>> have a two instance primary and a two instance standby. This is my
>> ultimate
>> goal but achieving success by shutting off PRIM after a switchover is a
>> good
>> start.
>> 3. I read many who recommend complimenting a switchover with a DNS update
>> or a
>> quick tnsnames.ora update to fool the client into "thinking" it is still
>> connecting to the same database it always was. I recognize this is *a*
>> solution but I'm looking for something more elegant that is inline with
>> what
>> Oracle describes in the documentation.
>
>

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