oracle settings archive

Oracle is a commonly used database management system that is widely used in enterprise data storage and processing. When the incremental log (redo log) of the data in the database reaches a certain number, it can be archived and the incremental log files can be moved from the online disk to the offline storage medium to facilitate backup, recovery and disaster recovery. usage of.

Oracle's archive mode is very simple. You only need to add a parameter in the initialization parameter file and enable "archive mode" to automatically move the archive files to other media after each database recovery is completed.

This article will introduce you how to set the archive mode in Oracle.

1. Types of archive modes

There are two types of Oracle’s archive modes: NOARCHIVELOG mode and ARCHIVELOG mode.

In NOARCHIVELOG mode, Oracle only saves the database's incremental logs to online disks, not to offline storage media, and archive files cannot be used for disaster recovery. This mode is often used for small databases.

In ARCHIVELOG mode, Oracle saves incremental log files to offline storage media to facilitate backup, recovery, and disaster recovery. This mode is often used in large databases. For important data, it is recommended to use the archive mode to ensure data integrity.

2. Enable archive mode

To enable ARCHIVELOG mode, you first need to modify the initialization parameter file, that is, find and edit the init.ora file under ORACLE_HOME/dbs.

You can use the following editor to open the file:

vi $ORACLE_HOME/dbs/init.ora

Then add the following parameters in the file content:

log_archive_start = true
log_archive_dest = '/u01/app/oracle/admin/ORCL/arch'

Among them, the log_archive_start parameter indicates starting the archive, and the log_archive_dest parameter indicates the destination of the archive file. In this example, the archive will be saved to the /u01/app/oracle/admin/ORCL/arch directory.

After completing the modification, you need to restart the database for it to take effect.

3. Deactivate the archive mode

To deactivate the archive mode, you can perform the following steps:

1. Connect to the Oracle instance in SQL*Plus, and Query the current archive mode of the database.

SQL> archive log list;
Database log mode No Archive Mode
Automatic archival Disabled
Archive destination USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence 3
Current log sequence 4

2. If the current archiving mode is NOARCHIVELOG mode, no operation is required. If it is ARCHIVELOG mode, you need to perform the following steps:

SQL> shutdown immediate;
SQL> startup mount;
SQL> alter database noarchivelog;
SQL> alter database open ;

3. Modify the parameter file and set the log_archive_start parameter to false.

4. Archive file management

In archive mode, Oracle will automatically move incremental logs to offline storage media. Administrators can use the following commands to view, manage and delete archive files:

1. Query the status of the current archive file:

SQL> archive log list;
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /u01/app/oracle/fast_recovery_area/ORCL/archivelog

2. View a list of all archive files:

SQL> select * from v$archived_log;

3. Delete archive files that have been backed up:

SQL> delete archivelog all backed up 1 times to device type disk;

4. View the size of the archive file:

SQL> select name, blocks*block_size/1024/1024 as Size_MB from v$archived_log;

Summary

Through the introduction of this article, we learned how to set the archive mode in Oracle. Enabling archive mode can ensure data integrity and is recommended for important data. When using the archive mode, administrators need to manage and delete expired archive files in a timely manner to avoid taking up disk space.

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