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5.	Why do you need to have data guard?
	Data guard setup ensures that another database is available as a copy of production database at almost real time. As a result, we have higher protection for enterprise data and the new database is available very quickly without the need to actually restore and recover from backup. Therefore, data guard offers an excellent disaster recovery solution.
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6.	Is there any difference in the data changes in primary and secondary database?
	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 the following synchronization modes: 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. 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. 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 us written to an online redo log of the primary database without waiting to transfer the redo log to the standby database.
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7.	What is the maximum number of standby database that can be associated with a production database?
	A production database can have maximum of nine standby databases.
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8.	How can you find out whether a database is primary or standby?
	You can query the v$database view. The database_role column provides the relevant information.
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