Hello Max,
I don't think this parameter can be considered in this generation when
thinking of high availability solutions. As simple if you want to achieve
real-time apply then ignore the parameter.
There are other options available to overcome the parameter
archive_lag_target....they are
1) Switching time --> In that case why can't you consider redo log file
sizing based on the switch count per hour?
2) Delay --> If you want to ensure your standby should lag with primary for
15 or 30 minutes, then you can consider delay_mins attribute for each
destination... The best part is if you have two standby databases...then
one standby you can configure Real-Time apply and the other with delay_mins
, so that data can be restored even though you have missed/truncate the
table on primary.
archive_lag_target where can be used in various situations like downstream
capture but it doesn't make sense for your requirement and not think of it.
Please let us know if any questions.
Thank You.
On Mon, Dec 21, 2015 at 12:26 PM, Mladen Gogala <gogala.mladen@xxxxxxxxx>
wrote:
On 12/20/2015 07:01 PM, kathryn axelrod wrote:
You are correct; real time apply is a free feature of ee data guard. It
simply changes the process from waiting for actual archive logs to sending
'in real time' using redo logs.
Yes, you are correct:
7.2.1 Using Real-Time Apply to Apply Redo Data Immediately
If the real-time apply feature is enabled, apply services can apply redo
data as it is received, without waiting for the current standby redo log
file to be archived. This results in faster switchover and failover times
because the standby redo log files have been applied already to the standby
database by the time the failover or switchover begins.
Use the ALTER DATABASE statement to enable the real-time apply feature,
as follows:
-
For physical standby databases, issue the ALTER DATABASE RECOVER
MANAGED STANDBY DATABASE USING CURRENT LOGFILE statement.
-
For logical standby databases, issue the ALTER DATABASE START LOGICAL
STANDBY APPLY IMMEDIATE statement.
(
https://docs.oracle.com/cd/E11882_01/server.112/e41134/log_apply.htm#SBYDB0050
)
--
Mladen Gogala
Oracle DBAhttp://mgogala.freehostia.com
