Enabling ARCHIVELOG Mode

For High Availability features in Oracle you need to enable archivelog mode. When database is in ARCHIVELOG mode, redo logs are archived. These archivelog files are saved in a separate place and can be backed up. Archive logs are used by RMAN, Data Guard, Flashback and so on…

Log Miner, that is discussed in the next post, uses archive logs to show you the changes made to the database during some period of time.

If you are going to enable archivelog mode on a real database, it is better to shutdown database and make a cold backup. To save final noarchivelog mode backup.

Parameter that defines the location of archivelog files is LOG_ARCHIVE_DEST. You are able to set 10 different locations

for archivelogs: using log_archive_dest_1 through log_archive_dest_10 parameters.

The following system views provide us with the information about archiving:

V$DATABASE- identifies whether database is in ARCHIVELOG or NOARCHIVELOG mode.

SQL> select log_mode from v$database;

LOG_MODE
------------
ARCHIVELOG

V$ARCHIVED_LOG – displays historical archived log information from the control file. If you are using recovery catalog, then RC_ARCHIVED_LOG view contains similar information.

V$ARCHIVE_DEST- displays archivelog destinations, its status…

SQL> select DEST_NAME, STATUS, DESTINATION from V$ARCHIVE_DEST;

DEST_NAME                  STATUS    DESTINATION
------------------------- ---------- ---------------------------------------
LOG_ARCHIVE_DEST_1    VALID        C:\oracle\product\10.2.0\db_1\RDBMS
LOG_ARCHIVE_DEST_2    INACTIVE
…
LOG_ARCHIVE_DEST_10    INACTIVE

As you can see my archivelogs will go to “C:\oracle\product\10.2.0\db_1\RDBMS”.

V$ARCHIVE_PROCESSES-Displays information about the state of the various archive processes for an instance.

V$BACKUP_REDOLOG- Contains information about any backups of archived logs. If you use a recovery catalog, then RC_BACKUP_REDOLOG contains similar information.V$LOG-Displays all redo log groups,their sizes,number of members,are they archived or not and their status.

>set ORACLE_SID=ORCL

>sqlplus sys/pass as sysdba

SQL> shutdown immediate;

SQL> startup mount;

SQL> alter database archivelog;

SQL> alter database open;

SQL> select log_mode from v$database;

LOG_MODE
------------
ARCHIVELOG