Lesson 1

Up to this point we have learned to set up a database to facilitate archiving of redo log files. In this module we will learn to set up a database to provide for both

1. manual and
2. automatic

archiving of redo log files. By the end of this lesson you should be familiar with the following topics:

1. Normal ARCH processing
2. Manual archiving of redo log files
3. Automatic archive log file options
4. Obtaining archive log information

Also included is a brief discussion on the use of standby databases. While the Oracle8 DBA certification exam does not test you on this topic, it is an important consideration when formulating a complete backup and recovery plan. Often the cost to maintain a standby database can be justified by doing an analysis of lost revenue incurred during the recovery of your primary database.
The next lesson discusses archiving your redo log files.

Here's a breakdown of manual and automatic archiving options specifically for backup purposes in Oracle 19c:

1. Manual Archiving** * **User-Initiated:** The DBA directly issues commands to archive redo log files. This requires knowing the exact commands and file locations. * **Control:** Provides granular control over which redo log files are archived and when. * **When to Use:** * Infrequent or specific backup needs. * Smaller databases where manual control is feasible. * When strict timing around archiving is required for a tailored backup process.
2. Automatic Archiving** * **Background Processes:** Oracle's ARCn (Archiver) processes automatically handle the archiving of redo log files as they are filled. * **Configuration:** You set this up mainly by: * **ARCHIVELOG Mode:** Enabling this mode is essential for automatic archiving. * **LOG_ARCHIVE_DEST_n Parameters:** These define where archived logs should be stored (disk locations, flash recovery area). * **Benefits:** * Convenient, always-on protection ensuring redo logs are backed up. * Reduces manual DBA intervention. * Highly recommended for most production environments.

How Automatic and Manual Archiving Work Together for Backups It's not an either/or situation. Here's how they relate:

• Foundation:** Automatic archiving lays the groundwork for consistent backups by ensuring redo logs (which contain all database changes) are preserved.
• Backup Tools:** Backup tools like RMAN (Recovery Manager) can then use these archived logs in conjunction with datafile backups to provide point-in-time restoration capabilities.

Additional Considerations

• RMAN:** Oracle's Recovery Manager is a powerful tool that can utilize archived redo logs created by both automatic and manual archiving for more flexible backup and recovery.
• Retention Policies:** Think about how long you need to keep archived logs for your backup and recovery needs. This influences configuration settings.

By querying the V$INSTANCE view, you can determine the status of the archiver process. Run the following query:

SELECT archiver
FROM V$INSTANCE
ARCHIVE
-------
STARTED

A status of STARTED means that automatic archiving has been enabled for the database and that the ARCn process is running. If the value is STOPPED, this indicates that either manual archiving or no archiving is being performed.