Oracle Database 11 g - Online Public Access Catalog

CHAPTER 10 ■ DATA GUARD 425has to perform all the steps required to convert the physical standby database to the snapshotstandby database manually. In addition, you must perform the steps required to convert thesnapshot standby database to the physical standby database manually. These steps are significantlymore complicated in Oracle Database 10g Release 2 than in Oracle Database 11g. ManyDBAs are not aware that the snapshot standby database equivalent capability is available inOracle Database 10g Release 2. For complete details, please refer to the case study on Oracle’sMaximum Availability Architecture web site:http://www.oracle.com/technology/deploy/availability/htdocs/FNF_CaseStudy.htmlThe syntax to convert the snapshot physical database to the standby physical database isas follows:alter database convert to physical standby;Convert Back to Physical StandbySimilarly, the database must also be in a mounted state to convert to physical standby mode.If you are not in a mounted state, you will receive this error if you attempt to convert back to aphysical standby:SQL> alter database convert to physical standby;alter database convert to physical standby*ERROR at line 1:ORA-01126: database must be mounted in this instance and not open in any InstanceOnce you mount the database, you will be able to convert back to a physical standby, asshown here:SQL> alter database convert to physical standby;Database altered.Now you need to shut down the database again, mount or open the database, and restartmanaged recovery. The conversion process back to physical standby will discard all the changesthat were made while the database was in snapshot standby mode. As stated earlier, Oracleutilizes an implicit guaranteed restore point created earlier during the conversion from thephysical standby to the snapshot standby. Oracle issues a flashback database to the specificguaranteed restore point. Before the snapshot standby is converted to the physical standby,the guaranteed restore point is dropped. As the Data Guard database is brought back into thephysical standby mode, redo apply will apply all the redo data received while the database wasin the snapshot standby mode.Once the conversion back to physical standby is complete, the docs_dr table created in theearlier example disappears. In the following several queries, you will notice that the database isopened in read-only mode and the docs_dr table no longer exists: