Redo transferred by different modes to standby database:
Here in the standby database, if realtime apply is enabled, the redo data will be applied from the redolog file directly before archiving.Otherwise it will be archived and after it will be applied to the standby database.
And the redo applying(either by block wise or SQL wise) will be differed based on the physical and logical standby database.
1.Using Archiver Processes (ARCn) to Archive Redo Data
By default, redo transport services use ARCn processes to archive the online redo log files on the primary database. ARCn archival processing supports only the maximum performance level of data protection in Data Guard configurations. You must use the LGWR process to transmit redo data to standby locations that operate in other data protection modes.
Archiving to Local Destinations Before Archiving to Remote Destinations
2.Using the Log Writer Process (LGWR) to Archive Redo Data
You can optionally enable redo transport services to use the LGWR process to transmit redo data to remote destinations.
Using the LGWR process differs from ARCn processing (described in Section 5.3.1), because instead of waiting for the online redo log to switch at the primary database and then writing the entire archived redo log at the remote destination all at once, the LGWR process selects a standby redo log file at the standby site that reflects the log sequence number (and size) of the current online redo log file of the primary database. Then, as redo is generated at the primary database, it is also transmitted to the remote destination. The transmission to the remote destination will either be synchronous or asynchronous, based on whether the SYNC or the ASYNC attribute is set on the LOG_ARCHIVE_DEST_n parameter. Synchronous LGWR processing is required for the maximum protection and maximum availability modes of data protection in Data Guard configurations.
LGWR SYNC Archival to a Remote Destination with Standby Redo Log Files
Thanks & Regards,
Navaneeth
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