Re: Question on Oracle 11G RAC
- From: "Paul McManus" <Paul.McManus@xxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 10 Nov 2010 10:23:24 -0000
My attempts at answering the questions - apologies for lack of expert knowledge
and terminiology
>Hi, Thanks for the hint.
>I have a couple of questions.
>In a normal 2 node RAC database environment, will the two instances be
>always active ? I mean , will cache fusion takes place frequently , If my
>application and DMLs does not user parallelism ?
>I am just thinking , when will the high speed interconnect becomes busy
>with data transfer
Oracle RAC is always ACTIVE/ACTIVE and so cache fusion will always be passing
blocks.across your interconnect if sessions across instances are accessing the
same blocks. I imagine this will occur in your OLTP and Read Only configuration
if everyone is accessing the same data and therefore you cannot get away from
interconnect traffic - how much depends on the data, application and user
activitiy
Application Partitioning where users access different data across instances and
so do not need to share the same blocks is a method of minimising the
interconnect traffic
Like another poster said the offloading of read only and reporting activity to
a Standby or a distributed database of some description sounds like what you
want to achieve rather than using RAC
>If I can create a service one each node and associate to instance , How
>does my client tnsnames.ora looks like ? I could not figure out this.
Depends how you configure the service - specifically if you let the service
failover to an available instance in the event your preferred instance goes
down.
For example see the following TNSNAMES examples from 11gR2 (hence SCAN is used
but this could be substitiured for the full list of nodes available in your
cluster and the same info applies)
TEST1 is service that runs on both instances
TEST2 is configured to run on instance1 as preferred and instance2 as
available. The TNSNAMES entry does not indicate any instances - that is
abstracted from the users
test1 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = cluster-scan)(PORT = 1525))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = test1)
)
)
test2 =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = cluster-scan)(PORT = 1525))
(LOAD_BALANCE = YES)
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = test2)
(FAILOVER_MODE =
(TYPE = SELECT)(METHOD = BASIC)(RETRIES = 180)(DELAY = 5)
)
)
)
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