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

My understanding is the network setup is the same between the standbys. I didn't look at the network right away. :-) I made the changes suggested by Neil, but I'm still seeing the delay. Before I did a manual log switch, the delay was over 30 minutes. Not good for this critical production standby.

Sandy

On Thu, Jan 3, 2019 at 3:36 PM John Thomas <jt2354_at_gmail.com> wrote:

> There's no excessive delay between your primary and the lagging standby is
> there? Smaller pipe? Lots of network retries?
>
> Probably the second thing you checked...
>
> Regards,
>
> John
>
> On Thu, 3 Jan 2019 at 22:10, Sandra Becker <sbecker6925_at_gmail.com> wrote:
>
>> 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.
>>
>>

-- 
Sandy B.

--
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