With Dataguard, you do not need any fancy prep-work. Data Guard provides a comprehensive set of services that create, maintain, manage, and monitor one or more standby databases to enable production Oracle databases to survive disasters and data corruptions.

A Data Guard configuration consists of one production database and one or more standby databases. The databases in a Data Guard configuration are connected by Oracle Net and may be dispersed geographically. There are no restrictions on where the databases are located, provided they can communicate with each other. For example, you can have a standby database on the same system as the production database, along with two standby databases on other systems at remote locations.You can manage primary and standby databases using the SQL command-line interfaces or the Data Guard broker interfaces.

A physical standby provides a physically identical copy of the primary database, with on disk database structures that are identical to the primary database on a block-for-block basis. The database schema, including indexes, are the same. It is kept synchronized with the primary database, though Redo Apply, which recovers the redo data received from the primary database and applies the redo to the physical standby database.

A logical standby database is kept synchronized with the primary database though SQL Apply, which transforms the data in the redo received from the primary database into SQL statements and then executing the SQL statements on the standby database. A logical standby database can be used for other business purposes in addition to disaster recovery requirements. This allows users to access a logical standby database for queries and reporting purposes at any time. Also, using a logical standby database, you can upgrade Oracle Database software and patch sets with almost no downtime.

When setting up Dataguard, all you need is another server connected to the network with the same Oracle database binaries as production. All you will need to do is create a standby listener and entry in the tnsnames for each standby present. The new standby listener and tnsnames entry will be added to the production server's tnsnames and listener. Also, copy the product database tnsnames and listener entries into the standby server.

The redo data transmitted from the primary database is written on the standby system into standby redo log files, if configured, and then archived into archived redo log files. Log apply services automatically apply the redo data on the standby database to maintain consistency with the primary database. It also allows read-only access to the data.

Dataguard also lets you decide what type of DR you want: Protection, Availability, or Performance. Based on your options, you'll want Performance since you will want the High Availability but do not want your Primary failing over because of a network hiccup. Maximum Performance protection mode (the default) provides the highest level of data protection that is possible without affecting the performance of the primary database.

LS

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