What does “ALTER SYSTEM ARCHIVE LOG CURRENT” do?
The “ALTER SYSTEM ARCHIVE LOG CURRENT” command is a fundamental operation in Oracle Database management. It is used to specify the current online redo log file that should be archived. Understanding its purpose and usage is crucial for database administrators (DBAs) to ensure the integrity and recoverability of the database. In this article, we will delve into the details of this command and its implications on database performance and backup strategies.
The primary function of the “ALTER SYSTEM ARCHIVE LOG CURRENT” command is to inform the Oracle Database that the specified online redo log file should be archived. Online redo log files contain a record of all changes made to the database, and archiving these files is essential for maintaining the database’s recoverability. When an online redo log file becomes full, Oracle automatically archives it to a designated archive log destination.
How does it work?
When the “ALTER SYSTEM ARCHIVE LOG CURRENT” command is executed, Oracle performs the following steps:
1. Identify the current online redo log file: The command determines which online redo log file is currently active and should be archived.
2. Write the archive log header: Oracle writes an archive log header to the current online redo log file, indicating that the file should be archived.
3. Switch to the next online redo log file: Once the current online redo log file is marked for archiving, Oracle switches to the next available online redo log file, ensuring continuous logging of database changes.
4. Archive the current online redo log file: The database then archives the current online redo log file to the designated archive log destination, typically a disk or tape storage.
5. Update the control file: Oracle updates the control file to reflect the new archive log file, ensuring that the database can recover from any point in time.
By executing the “ALTER SYSTEM ARCHIVE LOG CURRENT” command, DBAs can manually archive online redo log files when needed, for example, in cases where automatic archiving is not functioning correctly or when performing certain maintenance tasks.
Importance of proper archiving
Proper archiving of online redo log files is crucial for several reasons:
1. Database recoverability: Archiving ensures that all changes made to the database are recorded and can be restored in case of data loss or corruption.
2. Performance optimization: By regularly archiving online redo log files, the database can free up space in the online redo log files, preventing performance degradation due to log file growth.
3. Point-in-time recovery: Archiving allows DBAs to perform point-in-time recovery, which is essential for recovering the database to a specific point in time before a failure or corruption occurred.
4. Backup strategy: Archiving online redo log files is an integral part of a comprehensive backup strategy, ensuring that the database can be restored to a consistent state after a disaster.
In conclusion, the “ALTER SYSTEM ARCHIVE LOG CURRENT” command is a vital tool for DBAs to maintain the integrity and recoverability of their Oracle databases. Understanding its purpose, usage, and implications on database performance and backup strategies is essential for ensuring the smooth operation of a database environment.
