Important situations of Oracle Dataguard
* Nologging or unrecoverable operations are not applied to standby – so be cautious in using those options. Alarming data block corruption error messages are reported if a user attempts to access any nologging or unrecoverable data blocks.
* ‘Drop tablespace’, ‘drop datafile’, ‘rename datafile’, and add/drop online redo log files operations need done on both nodes manually.
* Initialization parameter changes need done on both nodes manually.
* For databases upgrades, the software in the new ORACLE_HOME must be separately installed on both nodes. The database part of the upgrade is carried out only on the primary database.
* Often Data Guard replication is suspended for a significant period of time during and following the primary database upgrade. That is done with DGMGRL> edit database ‘mydb_sby’ set state=’APPLY-OFF’ ;. The standby server is only * upgraded, and replication resumed, once the primary upgrade has been determined to be a success.
* For patches, the software/binaries in the ORACLE_HOME must be separately patched on both nodes. The database part of the patch (if any) is carried out only on the primary database.
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