Functions of standby redo log

Functions of standby redo log

We all know that dataguard has three data protection modes: maximum protection mode, maximum available mode, and maximum performance mode.
In the maximum protection mode, standby redo log must be used in the highest available mode. The highest performance mode is also recommended.
Standby redo log. What is the difference between using standby redo log and not using it?

Db Oracle 10.2.0.1 physical standby
/U09/standbyarchivelog is the path of standby_archive_dest
/U09/archivelog is the path of log_archive_dest_1

The following test results:
--------- 1
Configuration of log_archive_dest_2 in the master database:
Log_archive_dest_2 = 'service = dba01 arch ASYNC VALID_FOR = (ONLINE_LOGFILES, PRIMARY_ROLE) DB_UNIQUE_NAME = dba01'
Use standby redo log: no
Test results:
When switching logs from the master database, archived logs are uploaded to the standby_archive_dest path of the slave database, and the mrp process is used.
--------- 2
Configuration of log_archive_dest_2 in the master database:
Log_archive_dest_2 = 'service = dba01 arch ASYNC VALID_FOR = (ONLINE_LOGFILES, PRIMARY_ROLE) DB_UNIQUE_NAME = dba01'
Use standby redo log: yes
Test results:
When switching logs from the master database, archived logs are uploaded to the standby database's standby redolog. An archive is generated in the path log_archive_dest_1 and the mrp process is used.
---------- 3
Configuration of log_archive_dest_2 in the master database:
Log_archive_dest_2 = 'service = dba01 lgwr ASYNC VALID_FOR = (ONLINE_LOGFILES, PRIMARY_ROLE) DB_UNIQUE_NAME = dba01'
Use standby redo log: no
Test results:
The standby standby_archive_dest path contains an archive file corresponding to the current log file of the primary,
Mrp applies this archive file only when switching logs in the master database.
If the slave database is failover, log files that are not archived will not be applied.
---------- 4
Configuration of log_archive_dest_2 in the master database:
Log_archive_dest_2 = 'service = dba01 lgwr ASYNC VALID_FOR = (ONLINE_LOGFILES, PRIMARY_ROLE) DB_UNIQUE_NAME = dba01'
Use standby redo log: yes
Test results:
The current log of the master database is uploaded to the standby redo log. The standby redo log is archived to the path of log_archive_dest_1 during archiving.
Mrp applies this standby redo log only when the master database logs are switched.
If the standby database is failover, the current standby redolog will be applied.

Conclusion:
If archive is transmitted using arch, there is no difference between standby redo logs because all logs to be uploaded are archived logs.
Use logwr to transfer archives. If the standby database fails to execute failover without the standby redo log, only the logs archived in the primary database are applied. If the archive is not performed, the files uploaded to the standby database are uploaded, it is also not applicable;
Use logwr to transfer archives. If the standby database executes failover when there is a standby redo log, not only archived logs and Unarchived standby redo logs will be applied.
Log can also be applied. This reduces data loss. I think this is why standby redo log must be used for maximum protection and maximum availability ~

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