RE: Data Guard - Fast Start failover
- From: Michael Schmitt <mschmitt@xxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 27 May 2010 12:14:07 -0500
We have a few systems that connect via jdbc connection strings and the
application groups were not able to alter those connection strings. Therefore,
we setup a hostname alias/IP that gets passed to whichever server is currently
running the primary. We setup an "after db role change" trigger that executes
a script on the server to grab the hostname/IP. Therefore, whenever the
primary changes the hostname alias gets changed as well. We keep the database
name the same and use services for the DB_UNIQUE_NAME
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of kathryn axelrod
Sent: Thursday, May 27, 2010 1:30 AM
To: Ram K
Cc: oracle-l
Subject: Re: Data Guard - Fast Start failover
Hi Ram,
Both actually. If you set up the observer with DGMGRL, you can only put it in
one location. However, if you set it up with OEM (one of the few worthwhile
features of OEM that doesn't cost extra), you get to set up a main observer And
a backup observer. Thus if the main observer goes down, the backup takes over.
Very nifty!
As for the tnsnames, this too is pretty spiffy. I think it's easiest to explain
with a setup example...
Create your tnsnames:
mydb =
(DESCRIPTION=(ADDRESS_LIST=(LOAD_BALANCE=off)(FAILOVER=ON)(ADDRESS=(PROTOCOL=tcp)(HOST=host1)(PORT=1521))(ADDRESS=(PROTOCOL=tcp)(HOST=host2)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=mydb.mydomain)))
Create a service:
exec dbms_service.create_service(service_name=>'mydb',network_name=>'mydb');
Create a trigger:
after startup on database
declare
role varchar (30);
begin
select database_role into role from v$database;
if role='PRIMARY' then
dbms_service.start_service('mydb');
else
dbms_service.stop_Service('mydb');
end if;
end;
The two issues with the failover connection are that the server changes and the
db name changes. Without any special setup, one would need to have multiple tns
strings or update their tns string after every failover.
The above steps take care of these issues as the tns string makes it such that
if mydb can't be found on host1, it looks for it on host2. (Thus it doesn't
matter which server is housing the primary.) And the service name/trigger combo
make it such that the primary db will always have the name of mydb (and the
standby never will). (Thus as long as you are connecting to 'mydb', you Will be
connecting to the primary.)
Hope this helps..
-k
Side note ->
We have yet to encounter any issues with DG (have DG on 9i, 10g, 11g and FSFO
on 10g & 11g) but I did just come across note 972207.1 which is definitely
worth reading before you pick your 11g version.
On Wed, May 26, 2010 at 6:47 PM, Ram K
<lambu999@xxxxxxxxx<mailto:lambu999@xxxxxxxxx>> wrote:
Thanks Kathryn. Did you install the observer in the DR site or at a third site?
Do the clients tnsnames need to be reconfigured in case of a failure when
connecting to the new primary.
On Wed, May 26, 2010 at 6:45 PM, kathryn axelrod
<kat.axe@xxxxxxxxx<mailto:kat.axe@xxxxxxxxx>> wrote:
You wouldn't even need FSFO if you have two hours of allowed downtime :)
FSFO works ~phenomenally~ well. Right now we have it running on 11.1.0.7 with
no issues...There is around 1minute of downtime if the primary crashes.
The only thing I'd throw out there is there are a few 11.1.0.7 DG specific
patches (see note 738538.1) that are recommended...Other than that, I truly
love DG/FSFO; it is amazing.
On Wed, May 26, 2010 at 3:41 PM, Ram K
<lambu999@xxxxxxxxx<mailto:lambu999@xxxxxxxxx>> wrote:
Hello,
We are planning on a new HA/DR solution for a new application that we are
building. Most of our databases sit on SAN which is synchronosuly replicated
via SRDF to a DR site. The users for this application want 2 hr window within
which the DB needs to available if it goes down. The vendor recommends
clustering, but I am also looking at Dataguard with Fast start failover. The
physical standby can be at the DR site. The DB will be on 11g.
Has anyone used 11g DG with FSF? Any specific issues? Does the DB come up
quickly without any problem if the primary DB goes down?
--
Thanks,
Ram.
--
Thanks,
Ram.
Other related posts:
