Oracle Data Guard Protection Modes ~ Atikh's DBA blog

There are three types of data guard protection modes in oracle

Before proceeding with next explaining these three modes, you can visit Standby database introduction to understand the purpose of standby database

All of these protection modes provides high data protection, but they differ in terms of availability and performance of primary database

Maximum Protection Mode

Maximum protection mode guarantees that no data loss will occur if primary database fails by any means
To provide this level of protection, redo data needs to recover a transaction must be written to both the online redo log and to at least one synchronized standby database before transaction commits.
To ensure that data loss can not occur, the primary database shutdown rather than continue processing transactions if it can not write to at lease one sync standby database
Recommendation

As this protection mode prioritizes data protection over primary database availability, oracle recommends to have minimum two standby database

Maximum availability Mode

This protection mode provides the highest level of data protection that is possible without affecting availability of the primary database.
Under normal operations, transactions to not commitment until all redo data needed to recover those transactions has been written to online redo log and based on user configuration one of the following is true

Redo has been received at standby database and acknowledge sent to primary
redo has been received and written to standby redo log and acknowledgement sent to primary

In case primary does not receive acknowledgement from at least one synchronized standby database then it operates as if it were maximum performance mode to preserve primary database availability until it is again able to write it to redo stream o synchronized standby database
To fully benefit from complete oracle data guard validation at the standby database,be sure to operate in real time apply mode so that redo changes are applied to standby database as fast as they are received.

Maximum Performance Mode

This protection mode provides highest level of data protection that is possible without affecting the performance of primary database.
This achieved by allowing transactions to commit as soon as all redo data generated by transactions has been written to the online log
Redo data is also written to one or mode standby databases but this is due to asynchronously with respect to transactions commitment, so primary database performance is unaffected by time required to transmit redo data and receive acknowledgement from a standby database.
This protection mode offers slightly less data protection than maximum availability and has minimal impact on primary performance
This is default protection mode in oracle.

Setting protection mode of primary database

Protection mode can be modified at any time as long as configuration meets requirements of mode.
Below are the steps for the same

Decide the protection among the above mentioned three modes
Verify the protection mode requirements with at lease one configuration standby database. Redo transport required for protection modes are

Verify if DB_UNIQUE_NAME is set as this is mandatory parameter for data guard configuration
Verify LOG_ARCHIVE_CONFIG parameter is set, its value includes a DG_CONFIG which includes DB_UNIQUE_NAME of primary and standby database for example

LOG_ARCHIVE_LOG='DG_CONFIG=('PRIM','STDBY')'

alter database set standby database to maximum {availability|performance|protection};

select protection_mode from v$database;

Oracle Data Guard Protection Modes