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@xxxxxxxxxxxxx <oracle-l-bounce@xxxxxxxxxxxxx> on behalf
of Sandra Becker <sbecker6925@xxxxxxxxx>
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.