Data Guard Basic

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 Summary

What is Data Guard

What is primary database

What is standby database:-

Standby database types:-

Data guard services:-

Oracle Data guard Production mode:

 

What is Data Guard:-

Oracle Data guard is provide the a comprehensive set of services that high availability, data production and distorter recovery

Oracle Data guard maintain the standby database its copy for the production database.

If production DB is unavailable because planned/unplanned activity standby database will become a production database role.

Planned (Switchover / Switchback) Unplanned (Failover)

 

What is primary database:-

Primary database is our production database

It can be either single instance/RAC database.

 

What is standby database:-

Standby database is copy of the production database.

 

Standby database types:-

Physical standby Database

Logical standby Database

Snapshot standby Database

 

Physical standby Database

Physical standby database is exact bloc for block copy of the production DB

The Physical standby database kept synchronized with primary database via redo apply.

When primary database generates redo entries, those redo are transferred to standby database and then redo is applied to standby database.

Logical standby Database

Logical database contain the same logical information from production database.

Logical standby database can be used to data production and reporting operations

The Logical database kept synchronized with primary database via sql Apply.

When primary database generates any redo entries it is transferred to standby database and then redo data are converted into SQL statements and then those SQL statements are applied to standby database.

This is allows to users to access the standby database queries and reporting any time.

 

Snapshot standby Database

Snapshot standby database is a fully updatable standby database.

A snapshot standby database receives and archives, but does not apply, redo data from its primary database

Redo data received from the primary database is applied when a snapshot standby database is converted back into a physical standby database, after discarding all local updates to the snapshot standby database.

 

Data guard services:-

Oracle Data Guard uses Redo Transport Services and Apply Services to manage the transmission of redo data, the application of redo data, and changes to the database roles.

 

Redo Transport Services:-

Its control the automated transfer of the redo data from production to standby database to one or more archive destination.

Its primary database side activity

Redo Transport Services Perform following actives

Transfer the redo data from the primary database to standby database.

Manage the process of resolving any gaps in the archived redo log files.

Automatically detect the missing/Corrupted archive redo log files from primary database.

 

Apply Services:-

Automatically apply the redo data on the standby database to maintain consistency with the primary database.

Its Standby database side activity


Redo apply -> physical standby databases, which applies redo data on the standby database using standard recovery mechanism


SQL apply -> Logical standby databases, which first transforms the received redo data into SQL statements and then executes the generated SQL statements on the logical standby database Help of MRP services apply all the redo changes in standby DB.

 

Role Transitions:-

Oracle Data Guard, We can change the role of a database using either a switchover or a failover operation.

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