New Features in Oracle Database 10g Release 2

Following is a brief summary of the Data Guard features that will be introduced in Oracle 10g Release 2.

Automatic Failover

New with Oracle 10g Database Release 2, you can invoke fast-start failover to automatically failover to a designated synchronized standby database in the event of loss of the primary database. In previous versions (including 10g Release 1), manual commands were still needed to complete the failover process to a standby database. Now there is no need for manual intervention in case of a major catastrophe.

Also, after a fast-start failover occurs, the old primary database is automatically reconfigured as a new standby database upon reconnection to the configuration. Keep in mind, however, that you still may need the use of Flashback Database to get your old primary in sync with the new primary; those steps are the same as in 10g Release 1.

Faster Redo Apply Failover

Oracle 10g Release 2 allows you to failover a physical standby database to the primary database role without doing a database restart, as long as the physical standby database has never been opened as read-only.

Flashback Database Across Switchovers

Oracle 10g Release 2 allows you to flashback the primary and standby databases to a point in time or System Change Number (SCN) prior to a switchover operation using Flashback Database. When you use this feature of Flashback Database on a physical standby, the standby role is preserved; when used on a logical standby, however, the role is changed to what it was at the target time or SCN. This feature extends the protection against user or logical errors.

Asynchronous Redo Transmission

Asynchronous redo transmission using the log writer process (LGWR ASYNC) has been improved to reduce the performance effect on the primary database. During asynchronous redo transmission, the network server (LNS) process transmits redo data out of the online redo log files on the primary database and no longer interacts directly with the log writer process. This change in behavior allows the log writer process to archive redo data to the current online redo log file and continue processing the next request without waiting for network I/O to complete.

SQL Apply

Oracle 10g Release 2 also introduces even more useful new features with SQL Apply. Here is a short summary of these upcoming changes:

• Faster failover with SQL Apply. Failover operations to a logical standby will be much faster because it will be no longer necessary to restart the SQL Apply service as part of the failover operation.

• Optimized creation of logical standby database. The creation of logical standby databases no longer requires the creation of the logical standby control file, which could not be used by RMAN. With 10g Release 2, logical standby databases cannot be easily created from a physical standby database. This reduces the manual operations required for creating a logical standby database.

• Automatic deletion of applied archived redo logs. All archived redo log files that are applied on the logical standby database will be automatically removed by the SQL Apply service.

• Expanded IOT support. IOTs that contain LOB columns and overflow segments will be supported with SQL Apply.