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Oracle
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SELECT protection_mode
FROM v$database;
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Enable
There are three Data Guard protection modes:
Maximum Performance
Maximum Availability
Maximum Protection
Maximum Performance
Maximum Performance
This is the default protection mode.
"This protection mode provides the highest level of data protection that is possible without affecting the performance of a primary database. This is accomplished by allowing transactions to commit as soon as all redo data generated by those transactions has been written to the online log. Redo data is also written to one or more standby databases, but this is done asynchronously with respect to transaction commitment, so primary database performance is unaffected by the time required to transmit redo data and receive acknowledgement from a standby database. This protection mode offers slightly less data protection than maximum availability mode and has minimal impact on primary database performance." [1]
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;
NOTE: If you are not using the Broker, LOG_ARCHIVE_DEST_n must contain NOAFFIRM, ASYNC and DB_UNIQUE_NAME.Maximum Availability
Maximum Availability
"This protection mode provides the highest level of data protection that is possible without compromising the availability of a primary database. Under normal operations, transactions do not commit until all redo data needed to recover those transactions has been written to the online redo log AND based on user configuration, one of the following is true:* redo has been received at the standby, I/O to the standby redo log has been initiated, and acknowledgement sent back to primary* redo has been received and written to standby redo log at the standby and acknowledgement sent back to primaryIf the primary does not receive acknowledgement from at least one synchronized standby, then it operates as if it were in maximum performance mode to preserve primary database availability until it is again able to write its redo stream to a synchronized standby database." [1]
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVAILABILITY;
Maximum Protection
Maximum Protection
"Maximum protection is similar to maximum availability but provides an additional level of data protection in the event of multiple failure events. Unlike maximum availability, which allows the primary to continue processing if it is unable to receive acknowledgement from a standby database, maximum protection shuts the primary database down rather than allowing it to continue processing transactions that are unprotected.Because this data protection mode prioritizes data protection over primary database availability, Oracle recommends that a minimum of two standby databases be used to protect a primary database that runs in maximum protection mode to prevent a single standby database failure from causing the primary database to shut down." [1]
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PROTECTION;
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