Re: One primary with two physical standbys exhibiting different behavior with regard to lag

Thanks, Andrew. That's one of the first things I checked. It's the same on both standbys.

Sandy

On Thu, Jan 3, 2019 at 2:47 PM Andrew Kerber <andrew.kerber_at_gmail.com> wrote:

> Neil most likely spotted the problem. But you should also check to make
> sure that the protection mode is the same on both standbys.If the instance
> that is behind is using the maximum performance (async) mode it can run a
> ways behind the primary.
>
> On Thu, Jan 3, 2019 at 3:36 PM Neil Chandler <neil_chandler_at_hotmail.com>
> wrote:
>
>> Sandy,
>>
>> Have you checked the Standby Redo logs? There's a slight (annoying)
>> change in Oracle 12.1 onwards which means that Standby Redo logs get
>> created with Thread 0 instead of Thread 1 by default (for a single instance
>> database). Redo can only use Standby Redo when the threads are the same. If
>> this is RAC you need Standby Redo for each thread - and you must have 1
>> more Standby Redo than Online Redo for each thread.
>>
>> By coincidence, I wrote a blog post about this 10 minutes ago.
>>
>> https://chandlerdba.com/2019/01/03/data-guard-unexpected-lag/
>>
>> regards
>>
>> Neil Chandler
>> Database Guy. Knows Things.
>>
>> ------------------------------
>> *From:* oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> on
>> behalf of Sandra Becker <sbecker6925_at_gmail.com>
>> *Sent:* 03 January 2019 20:29
>> *To:* oracle-l
>> *Subject:* One primary with two physical standbys exhibiting different
>> behavior with regard to lag
>>
>> Oracle 12.1.0.2
>> RHEL7
>>
>> To begin with, I have not worked much at all with standby databases, so
>> my knowledge is somewhat lacking.
>>
>> For business reasons, we have a primary database with two physical
>> standbys. Everything is configured in dgmgrl and enabled. Monitoring with
>> EM13c is reporting the lag times, so all looks good for basic setup and
>> monitoring. We seem to have significant lag at times on one of the
>> standbys, as much as 20 minutes. When looking at v$managed_standby, we see
>> the status as "WAIT_FOR_LOG". The other standby never seems to be more
>> that a few seconds behind, if at all, and the status is "APPLYING_LOG".
>>
>> Is this normal? I've been researching, but haven't found an answer yet.
>> I didn't create or start the standby databases, so I don't have any idea
>> what was actually done that could be causing this behavior. Any
>> suggestions would be appreciated.
>>
>> Thank you,
>>
>> --
>> Sandy B.
>>
>>
>
> --
> Andrew W. Kerber
>
> 'If at first you dont succeed, dont take up skydiving.'
>

-- 
Sandy B.

--
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