Database Reference
In-Depth Information
If everything went according to plan, you should get the prompt back a few seconds after issuing the statement.
To see if there are any irregularities or other problems, execute the show configuration command again:
DGMGRL> show configuration
Configuration - apress
Protection Mode: MaxPerformance
Databases:
CDB1DCA - Primary database
CDB1DCB - Physical standby database
CDB1DCC - Physical standby database
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS
The most commonly reported problems at this stage are missing server parameter files on either database,
or missing standby redo logs. There should be no problems here at this stage if you followed the instructions in the
chapter.
Changing the protection mode to maximum availability
You read in the previous chapter's section about protection modes that you need to set the log transfer mode to SYNC
if you want any of the higher protection levels. With synchronous shipping of redo the speed at which a database's
commit statement completes partially depends on the network latency as well. If it takes considerable time for
a network packet to travel to a standby database the overall commit latency will suffer too. The advantage of the
synchronous transfer mode though is a better protection from data loss.
The protection mode Maximum Availability seems to be the best compromise of data protection and
continuity of service. To enable it, the databases in the Data Guard configuration need to be switched to ship redo
synchronously. Connected to the Broker command line utility, you need to update the LogXptMode database
property. You can see the example here:
DGMGRL> edit database "CDB1DCA" set property LogXptMode=Sync;
Property "logxptmode" updated
DGMGRL> edit database "CDB1DCB" set property LogXptMode=Sync;
Property "logxptmode"
You may have noticed that the third standby, which is configured to delay the application of redo for 30 minutes,
has not had the log transport property changed. In a delayed configuration it does not matter much if the redo
information is shipped asynchronously or synchronously.
As soon as the log ship property has been updated you can change the protection mode. The “edit configuration”
command helps you do this. In the example the protection mode is upgraded from maximum performance to
maximum availability. This upgrade does not require a restart of any database in the configuration.
DGMGRL> edit configuration set protection mode as maxAvailability;
Succeeded.
DGMGRL> show configuration
Configuration - apress
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