Data Guard Protection Modes

ORACLE_DATAGUARD_Data Guard Protection Modes

TRANSPORT: Data Guard Protection Modes

MAXIMUM PROTECTION 

Thisprotection mode guarantees that no data loss will occur if theprimary database fails. To provide this level of protection, the redo dataneeded to recover each transaction must be written to both the local onlineredo log and to a standby redo log on at least one standby database before thetransaction commits. To ensure that data loss cannot occur, the primarydatabase will shut down if a fault prevents it from writing its redo stream toat least one synchronized standby database.

To participate in MAXIMUM PROTECTION the followingrequirements must be met:

RedoArchival Process : LGWR

NetworkTransmission mode : SYNC

DiskWrite Option : AFFIRM

StandbyRedo Logs : Yes

StandbyDatabase Type :  Physical Only in 9i, Physical AND Logical in 10g

Becausethis data protection mode prioritizes data protection over primary databaseavailability, Oracle recommends that a minimum oftwo standby databases beused to protect a primary database that runs in maximum protection mode toprevent a single standby database failure from causing the primary database toshut down.

 

MAXIMUM AVAILABILITY

Thisprotection mode provides the highest level of data protection that is possiblewithout affecting theavailability of the primary database.Like maximum protection mode, transactions do not commit until all redo dataneeded to recover those transactions has been written to the online redo logand to at least one synchronized standby database. Unlike maximum protectionmode, the primary database will not shut down if a fault prevents it fromwriting its redo stream to a synchronized standby database. Instead, theprimary database will operate in RESYNCHRONIZATION until the fault is correctedand all log gaps have been resolved. When all log gaps have been resolved, theprimary database automatically resumes operating in maximum availability mode.

This mode ensures that no data loss will occur if the primary database fails,but only if a second fault does not prevent a complete set of redo data frombeing sent from the primary database to at least one standby database.

To participate in MAXIMUM AVAILABILITY the followingrequirements must be met:

RedoArchival Process : LGWR

NetworkTransmission mode : SYNC

Disk WriteOption : AFFIRM

StandbyRedo Logs : Yes

StandbyDatabase Type : Physical and Logical

 

MAXIMUM PERFORMANCE

Thisprotection mode provides the highest level of data protection that is possiblewithout affecting the performance of the primary database. This is accomplishedby allowing a transaction to commit as soon as the redo data needed to recoverthat transaction is written to the local redo log. The primary database's redodata stream is also written to at least one standby database, but that redostream is written asynchronously with respect to the commitment of thetransactions that create the redo data.

When network links with sufficient bandwidth and latency are used, this modeprovides a level of data protection that approaches that of maximumavailability mode with minimal impact on primary database performance.

To participate in maximum performance the following requirements must be met:

RedoArchival Process : LGWR or ARCH

NetworkTransmission mode : ASYNC when using LGWR only 

DiskWrite Option : NOAFFIRM

StandbyRedo Logs : No, but recommended and required for Real-Time Apply

StandbyDatabase Type : Physical and Logical

 

The checking：

SQL> selectOPEN_MODE,PROTECTION_MODE,database_role from v$database;

Change the mode：

SQL> startup mount;

SQL> alter database set standby databaseto maximize availability|performance|protection