Data Guard instance Protection Modes Oracle Database Tips by Donald BurlesonDecember 9, 2015

Oracle Data Guard

Oracle instance Protection Modes

Protecting data of the primary database in case of any disaster is the whole purpose of Data Guard technology. Data Guard provides different levels of protection modes that can be configured to suit the need. Importance of data in the database and the ability to recover it from other sources are vital factors in deciding the protection mode. The higher the level of data protection, the more the performance of the primary database will be affected. Therefore, the performance requirement of the environment is another factor to consider.

The database protection mode is established using the attributes of log transport services which has already been covered in detail. This section will present the combined usage of those attributes to implement a data protection strategy. The protection modes have changed significantly between Oracle 9i Release 1 and Release 2, and will be described separately in this section.

The data protection modes in Release 1 of Oracle9i can be categorized into the following four classes:

• Guaranteed Protection
   

• Instant Protection
   

• Rapid Protection
   

• Delayed Protection

These four protection modes offer varying degrees of synchronization between the primary and the standby database and the amount of data loss during disaster recovery.

Guaranteed Protection Mode

The guaranteed protection mode falls in the category of 'no-data-divergence'. In this case, a transaction on the primary database is not acknowledged as complete until one of the participating standby databases has received the redo data for recovery. The primary database shuts down if the redo data cannot be transmitted to at least one participating standby database. This mode offers the highest level of data protection at the expense of performance and availability of the primary database. The following attributes of the log_archive_dest_n parameter should be used to setup log transfer service for guaranteed protection mode:

LOG_ARCHIVE_DEST_3='SERVICE=appsstdby1 LGWR SYNC AFFIRM';

Moreover, create standby redo logs need to be created on the Oracle instance so it can receive redo data synchronously from the primary database. The following statement should be executed on the primary database to set the failure resolution policy: