Data Guard

Data Guard sample physical standby example Donald K. Burleson

A Sample Data Guard Configuration

This section presents a sample configuration of standby databases. In figure 1.4, NetBillProd is a production database located in New York. This database serves all the database requests for a telecom billing application. The database has two standby databases on the same local area network (LAN). These standby databases are: NetBillPhy1 and NetBillLog1. NetBillPhy1 is the physical Oracle instance and NetBillLog1 is the logical standby database. Also, there is a physical Oracle instance NetBillPhy2 located in London, UK.

The production database, NetBillProd, and the NetBillPhy2 Oracle instance are connected over a wide area network (WAN). Although the production database and two of its standby databases reside on the same LAN, they do not share the same server or storage.

The first physical standby database, NetBillPhy1, is primarily used for switchover operation when the production database is undergoing maintenance operation. In this case, the backup is performed on the Oracle instance instead of the production database.

In this example, the billing system is sending data to another module residing in same database, which is used for nightly batch reporting. In this case, the database objects used for reporting can be segregated and used to create only those objects in the logical standby database, NetBillLog1.

A Sample Data Guard Configuration

Additionally, NetBillLog1 will have materialized views and indexes to speed up the reporting queries. In other words, NetBillLog1 will cater to all reporting requests, and the computing resources on the production database, NetBillProd, will be utilized in the completion of other tasks.

In case of a disaster where the primary production database is destroyed, there are two options. If the physical standby database, NetBillPhy1, is unaffected by the disaster, it can be activated to act as production database. Since the production database and this particular Oracle instance are on same LAN, there should not be any performance degradation; however, the performance factor largely depends on the computing resources of the Oracle instance as compared to the original production database.

If the production database site is completely destroyed and all servers in the location are affected, the second standby database, NetBillPhy2 located in London, UK, can be activated to act as the production database. Since NetBillPhy2 is not on the same LAN, there may be performance related issues when it starts serving the database requests. Again, the performance depends on the nature of the application. For an internet application, the effect on performance should be minimal.

The physical standby databases can be configured in any of the three data protection modes. The main factors influencing the selection of a data protection mode are the importance of data and the network bandwidth. In a LAN environment, the maximum protection or maximum availability mode will not show any performance degradation; however, in a WAN, this can have a significant impact.