The primary and standby databases can be completely synchronized or partially synchronized in terms of data based on the synchronization mode set for data guard, which offers
i.Maximum protection mode —Specifies that a data change on primary database is acknowledged only when it is available to standby database at least in the form of redo log information. In this mode, primary database shuts down if at least one standby database cannot be updated.'
ii.Maximum availability mode —Specifies that a transaction cannot be committed unless redo logs of at least one standby database are completely synchronized with primary database. However, this mode is more tolerant in terms of fault in updating standby database. It allows the primary database to function temporarily in maximum performance mode until such error is resolved and gaps are analyzed.
iii.Maximum performance mode —Allows slight delay in updating standby database; and therefore, offers certain performance gain. In this mode, transaction can be committed as long as the change is written to an online redo log of the primary database without waiting to transfer the redo log to the standby database.
i.Maximum protection mode —Specifies that a data change on primary database is acknowledged only when it is available to standby database at least in the form of redo log information. In this mode, primary database shuts down if at least one standby database cannot be updated.'
ii.Maximum availability mode —Specifies that a transaction cannot be committed unless redo logs of at least one standby database are completely synchronized with primary database. However, this mode is more tolerant in terms of fault in updating standby database. It allows the primary database to function temporarily in maximum performance mode until such error is resolved and gaps are analyzed.
iii.Maximum performance mode —Allows slight delay in updating standby database; and therefore, offers certain performance gain. In this mode, transaction can be committed as long as the change is written to an online redo log of the primary database without waiting to transfer the redo log to the standby database.