Re: Why I don't Like Data Guard was Re: Oracle RAC thread

From: Andrew Kerber <andrew.kerber_at_gmail.com>
Date: Tue, 7 Jan 2014 10:45:00 -0600
Message-ID: <CAJvnOJaCJzomeVUupvfL4G7EwUWRk7C3-o32Jpq_cAUA+D56MA_at_mail.gmail.com>

I am not trying to start an argument, but I do want to point out that the steps to change a dataguard IP address are trivial. Once you change it on the server, you change it on the service name entry in the tns file. Done. If you make the mistake of using an IP address in the log_archive_dest_2 setting, then you have a problem. But using a service name option, the change is trivial.

Also, I am not clear how using scripts in any way changes the maintenance requirements. Whether using scripts or dataguard, you still need to check the status daily, and make sure logs are getting applied, and make sure you have enough archive log space, etc. Also, using dataguard you know your archive logs on your primary are not getting deleted before being shipped to your standby, which gives an added level of safety.

However, I do admit that if cost is your primary consideration, using standard edition with manual apply is cheaper, I just dont see that it is any easier.

On Tue, Jan 7, 2014 at 9:49 AM, Dave Morgan <oracle_at_1001111.com> wrote:

> On 01/02/2014 08:55 AM, Jeremy Schneider wrote:
>
>> Dave, I'm curious why you would opt for manual log ship and apply instead
>> of Data Guard?
>> Also, why do you say that "Data Guard is expensive"? Do you just mean
>> that enterprise edition is expensive?
>> -Jeremy
>>
>
> Thanks for the intro ;)
>
> On Mon, Dec 30, 2013 at 1:15 PM, Dave Morgan <oracle_at_1001111.com <mailto:
>> oracle_at_1001111.com>> wrote:
>> On Mon, Dec 23, 2013 at 8:07 PM, Chris King <ckaj111_at_yahoo.ca<mailto:
>> ckaj111_at_yahoo.ca>> wrote:
>> We're architecting a new system, and will need 99.5%
>> availability. Looking
>>
>> I believe this is the wrong metric to use. As others have pointed out
>> it is equivalent to
>> ~40hours/year. The correct question is what is the longest outage the
>> business can afford
>> for any single event?
>>
>> 15 minutes, 1 hour, 4 hours?
>>
>> If the business claims less than 15 minutes they should have real
>> reasons, DataGuard is expensive.
>>
>> My standard is a simple automatic log ship and apply system from the
>> old days. Train the
>> sysadmins to do the failure-over and you can meet a 15 minute
>> deadline during business hours.
>>
>> Cheap, easy, tested, robust, runs with 3-5 hours of scheduled
>> downtime per year. Every year.
>>
>>
> First, yes Enterprise edition is expensive, however, if you NEED what Data
> Guard supplies then it is cheap at the price.
> However, Data Guard has a much higher maintenance cost also. This
> maintenance cost is extra administrator time.
>
> Data Guards are dependent on each other. Data Guards require knowledgeable
> DBAs and sysadmins. In order
> to be really successful with Data Guard one needs sophisticated developers
> who can do TAF or
> auto-magically reread the tnsnames source upon connection failure. So for
> cases where the business can
> afford an outage of 15 minutes or so, I can provide a cheaper, more robust
> solution.
>
> Now that we know where not to use it, lets agree what Data Guard is for
> and when it should be used.
>
> Most businesses can afford an outage of 15-30 minutes. The only business
> that can't are those whose transactional
> databases are intimately involved in the sales process. Telecoms, banking,
> and airlines for example.
> Any time the business claims a need of < 15 minute outages make sure you
> understand why! Loss of revenue
> or real time access are usually the only real needs, almost everything
> else fails an ROI test.
>
> If the business has a valid need and DataGuard is chosen to meet it, the
> first objective , I think, is
> to be able to perform an automated fail over and the worst any of the
> "important" clients experience
> is a 30 second hiccup.
>
> How long is the above going to take? What are you going to use while
> building and testing the above
> architecture? What are the total man hours involved?
>
> I can build you a ship and apply system for the time of a single recovery
> and it will take far less admin time than
> a Data Guard system. The sysadmins can shut it down, move it, change IP
> address, whatever they want and as soon as
> it stands back up it starts working again, as if nothing happened. Shall
> we go through the steps required to
> change a Data Guard IP address?
>
> The ship and apply system is simple and easily understood.
> Nothing more than 2 sql scripts and 3 ten line shell scripts or windows
> batch files.
> The 2 databases are completely independent.
>
> Why would I use Data Guard when the business does not need "instantaneous"
> recovery?
> Why would I use Data Guard when the infrastructure supports synchronous
> writes between data centres?
>
> I do not consider more billable hours a valid reason :)
>
> Again I apologize for the aggressive tone of the "Why I Don't Like"
> subject line.
>
> TIA
> Dave
>
> --
> Dave Morgan
> Senior Consultant, 1001111 Alberta Limited
> dave.morgan_at_1001111.com
> 403 399 2442
>
> --
> Dave Morgan
> Senior Consultant, 1001111 Alberta Limited
> dave.morgan_at_1001111.com
> 403 399 2442
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

-- 
Andrew W. Kerber

'If at first you dont succeed, dont take up skydiving.'

--
http://www.freelists.org/webpage/oracle-l

Received on Tue Jan 07 2014 - 17:45:00 CET