Important situations of Oracle Data Guard
- 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.