Data Guard provides three types of Protection Mode:

1- Maximum Protection: This mode ensures that you will not lose any data in the event of a problem in the Primary Database because the Redo Data for any process will be written to both the Local Online Redo Log and the Standby Redo Log in at least one Standby Database before it is committed.

To ensure that you will not lose any data, the Primary Database will be shut down if it is unable to send Redo Data to at least one Remote Standby Redo Log.

2- Maximum Availability: This type provides you with the highest level of data protection without compromising the availability of the Primary Database. It is similar to the Protection Mode in that the processes are not installed until the Redo Data is written for these processes in both the Local Online Redo Log and the Standby Redo Log at least in the Standby Database, but this mode differs from the Protection Mode because the Primary Database is not closed if it is unable to write the Redo Data in the Remote Standby Redo Log, but the Primary Database operates in Maximum Performance until the problem is fixed and the vulnerabilities in the Redo Log Files will be fixed. Once all the vulnerabilities in the Redo Log Files are fixed, the Primary Database will operate again automatically in Maximum Availability mode.

This mode also ensures that you will not lose any data in the event of a problem in the Primary Database.

3- Maximum Performance: This is the default mode at the moment of creating the configuration, and it provides the highest possible level of data protection without affecting the performance of the Primary Database, by installing the processes as soon as the Redo Data is installed in the Local Online Redo Log, meaning that the processes in the Primary Database do not wait for the Redo Data to be received in the Standby Database to be installed in the Primary Database, but if any Standby Databases become unavailable, the processes will continue normally in the Primary Database and warning messages will be sent in the Alert Log.

So the processes may not be synchronized between the Primary and Standby Databases, and if a problem occurs in the Primary Database, we may lose some data that was installed in the Primary Database and was not installed in the Standby Database, but if the network is working well, the amount of lost data will be very small or zero.

This mode does not require the Standby Redo Log.

To activate the (Maximum Protection or Maximum Availability) mode, the following steps must be followed:

1- Create a Standby Redo Log

A Standby Redo Log must be created in at least one Standby Database.

STARTUP OPEN READ ONLY
ALTER DATABASE ADD STANDBY LOGFILE GROUP 4 
 ‘D:\ORACLE\PRODUCT\10.1.0\ORADATA\PRIM\REDO4.LOG’
size 10M;
ALTER DATABASE ADD STANDBY LOGFILE GROUP 5 
 ‘D:\ORACLE\PRODUCT\10.1.0\ORADATA\PRIM\REDO5.LOG’
size 10M;

Make sure that the size of the Standby Redo Log is equal to the Primary Redo Log.

2- Configure the LogXptMode property.

The LogXptMode property must be configured to take the value SYNC in all Standby Databases.

DGMGRL> EDIT DATABASE 'STAN' SET PROPERTY 'LogXptMode'='SYNC';

3- Finally, activate Protection Mode.

DGMGRL> EDIT CONFIGURATION SET PROTECTION MODE AS MAXAVAILABILITY;