Oracle Dataguard Protection modes

Oracle Dataguard Protection modes

There are three types of Protection Modes in Oracle Dataguard .

Maximum Availability

1. It provides highest level of protection of data without compromising availability of database. In this protection mode primary database’s transaction does not commit until that redo is transferred to one of synchronized database and acknowledged from standby process of redo data arrival.
2. Once transaction’s redo data is transferred and written to standby redo log files then RFS process sent a acknowledgement to primary database and then that transaction commits at primary database.
3. If the primary database cannot write its redo stream to at least one synchronized standby database, 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.

Maximum Performance

1. As its name says it provides maximum level of data  protection that a database can have without compromising performance of database.
2. This is default Protection modein dataguard.
3. Unlike Maximum Availability Protection mode, this mode allows transactions to commit as soon as all redo data generated by those transactions are written to online redo log files. Here , redo data is transferred to standby database in asynchronous way , so it doesn’t affect primary database’s performance.
4. This mode offers less data protection than Maximum Availability mode as there is no concept of acknowledgment of redo data written to standby redo log file at standby database.

But as the primary database is unaffected by this delay , it offers maximum performance.

Maximum Protection

1. This protection mode ensures zero data loss if primary database fails.
2. We have seen in Maximum Availability protection mode that if it cannot write to one of synchronized standby database it works as if it were in Maximum Performance mode  But here in Maximum Protection mode , if database can not write to one of synchronized standby database , Primary database will shut down as this prioritize protection of primary database than availability of data.
3. Note :Oracle recommends when you use this mode of protection , you should keep at least two standby database that runs in maximum protection mode to prevent a single standby database failure from causing the primary database to shut down.

In the Next article, we will see few redo transport attributes required for setting in different protection mode.