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This article mainly explains "how to understand standby redo". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "how to understand standby redo".

Settings:

1. Each standby redo log file should be at least as big as the redo log of primary database. For ease of management, Oracle recommends that the redo log of the master and slave libraries be set to the same size.

SQL > SELECT GROUP#, BYTES/1024/1024 M FROM V$LOG

2.Standby redo log group should have at least one more group than primary database's redo log group. You can query the v$log view in the primary library to determine how many groups of redo log groups there are in the main library.

Formula: nx+1 (n is the number of log groups, x is the number of nodes)

Note: (Oracle recommends that you also create a standby redo log in the primary library so that you can receive redo data immediately after switchover. )

Create:

SQL > alter database add standby logfile thread 1 group 5 size 50m size 6 size 50m group 7 size 50m; (rac)

SQL > ALTER DATABASE ADD STANDBY LOGFILE ('xxxxxxx') SIZE 500m; (one node)

Note: when redo log group is added to the main library, a corresponding standby redo log group must also be added to the standby library. Otherwise, standby database may be out of sync after switch log in the main database, shutdown.

Delete:

SQL > alter database drop standby logfile group X

View:

Execute the following SQL query in the standby library for each standby redo log size and the members of each group:

SQL > SELECT GROUP#, BYTES/1024/1024 M FROM V$STANDBY_LOG

Thank you for your reading, the above is the content of "how to understand standby redo", after the study of this article, I believe you have a deeper understanding of how to understand standby redo, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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