Oracle Data Guard 12c Interview Questions and Answers - 2

Question: 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.

Question: 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.

Question: 8

Explain the architecture of data guard?

Data guard architecture includes the following components:

Primary database – Refers to the production database.

Standby database – Refers to a copy of primary or production database. Data guard architecture may have more than one standby database.

Log transport service – Manages transfer of achieve log files from primary to standby database.

Network configuration – Refers to the network connection between primary and standby database. This connection is based on Oracle Net.

Log apply services – Applies archived logs to the standby database.

Role management services – manages the role change between primary and standby databases.

Data guard broker – Manages data guard creation process and monitors the data guard.

Question: 9

What happens when stand by database is not available?

If standby database is not available and the changes are made in primary database, then there will be a gap in the sequence of archive logs. The information about archive logs in these gaps can be found in the v$archieve_gap view.

Question: 10

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.