Oracle has been continuously improving on Oracle Active Data Guard since it was released. For instance, we saw automatic archived log shipping and apply introduced in 8i, while with 9i you are now able to configure your instance for zero data loss and switchover was first introduced. In 10g, we saw support for flashback database introduced, while 10g R2 gave us guaranteed restore points. 11g gave us snapshot standby, compress redo, and lost-write detection out of the box, while automatic block corruption repair was added in the second release of 11g. Now that Oracle has introduced Data Guard 12c, what should you expect to see improved, added or changed?
Here are the major ones:
1. Far Sync. This feature allows you to failover to a standby database even if it is remotely located in another site thousands of miles away. You do this without any data loss and without negatively affecting the performance of the primary database. Far Sync also keeps things simple and your costs down.
2. Fast Sync. This feature gives you the easiest way to improve the database performance when you have synchronous no data loss setups. When a standby database gets a redo in memory, it will check with the primary database, even without getting a disk I/O to a redo log file in the standby. Fast Sync then effectively reduces the total round trip time between the standby and primary, resulting in better primary database performance. You should know, however, that there is a minute chance that data loss would happen when you use Fast Sync. But Oracle assures you that these instances would be so rare and it has to happen when both databases fail milliseconds within each other.
3. Real-time Cascade. Real-time Cascade allows your standby database to immediately transmit a redo to another standby database even when it has yet to be archived in the redo log file. Before 12c, redo is only cascade after the standby redo log file has finished being archived locally.
4. SYSDG. SYSDG is an administration privilege wherein the user can only perform basic administration actions and tasks. As such, SYSDG privileges are limited to STARTUP, SHUTDOWN, ALTER DATABASE, ALTER SESSION, ALTER SYSTEM, CREATE RESTORE POINT, CREATE SESSION, DROP RESTORE POINT, FLASHBACK DATABASE, SELECT ANY DICTIONARY, DELETE, and EXECUTE.
Other minor features that were introduced in Oracle Active Data Guard 12c:
Data Manipulation Language operations are now permitted on global temporary tables on the standby.
You no longer have to add the USING CURRENT LOGFILE clause when you initiate real-time apply.
You can now use sequences in a Data Guard environment.
You no longer need to shut down all other primary database instance if you need to switchover from an Oracle Real Application Clusters primary database to a physical standby. Application continuity is now supported as well.
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