When a file is corrupted, database continue to work using other member of the redo log group. This is necessary for redundancy and consistency. There are logical Redo log groups on the database where the Redo log files are stored, and each group has 2 identical files.
#Wechat windows architecture database cache archive#
Once the corresponding archive logs have been applied, online redo logs can be applied to recover the data until the last time. You cannot open the database consistently without applying Archive Logs. If there is a damage to the database, archive files will also be required when returning from the backup. The database must be in archive mode in order to make a backup in online mode. If the database is in Archive mode, these files are archived periodically as a result of a switch operation. These files store all changes in the database, and as I mentioned above, the records accumulated in the Redo log buffer area are recorded here at regular intervals. Online Redo log Files: These files are physical files on the operating system where all transactions in the database are stored.
Storing records of transactions is required for recovery when the instance crashes. Periodically, records in the Redo log buffer area are written to the Online Redo log files by the LGWR process. When a user or an application initiates a transaction, the transaction is initially written to the Redo log buffer. Redo Log Buffer: The Oracle database stores each transaction’s record. Because when the buffer cache is emptied, all queries or transactions will make I / O from the physical disk, which means that our queries will slow down. However, you should not execute the above command in production systems unless required.
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