Archived Redo Log Files

                                          Introduction

 

It is the DBA's choice whether to run the database in ARCHIVELOG mode or in NOARCHIVELOG. If the database is running in archivelog mode, contents of the online redolog files are copied to an archive area by an Oracle background processes Archiver(ARCn). These archive files are known as the archived redolog files, archived redologs or simply archived redo. These files are sometimes referred to as the offline redolog files since they are not open during normal operation of the database and are required only during recovery. The redo log files (online and archived) are essential for database recovery since they contain information on all changes made to the database. If database is chosen to operate in NOARCHIVELOG mode, online backups and database recovery will not be possible.

Note:

LOG_ARCHIVE_START=TRUE, this parameter is obsolete in 10g and automatic archiving is enabled in 10g.

To Convert the database into ARCHIVELOG mode:

Enter the following parameters in the init<SID>.ora

SQL>SHUTDOWN IMMEDIATE

#for enabling the Archive log mode you have to shutdown the database with normal, immediate option.

$cd $ORACLE_HOME/dbs

$vi initDEMO.ora

LOG_ARCHIVE_DEST=/disk2/oradata/DEMO/ARCH

:wq!

$mkdir /disk2/oradata/DEMO/ARCH

$sqlplus "/as sysdba"

SQL>STARTUP MOUNT

SQL>ARCHIVE LOG LIST

The above command will show whether automatic archival is started are not and also whether the database is running in archive log mode is not. After paasing the above parameters in init<SID>.ora automatic archival will be started but the database will be still in NOARCHIVELOG mode. The following command will convert the database into ARCHIVELOG mode.

SQL>ALTER DATABASE ARCHIVELOG;

SQL>ALTER DATABASE OPEN;

Data Dictionary Views you can query:

-V$ARCHIVED_LOG

-V$ARCHIVE_DEST

-V$ARCHIVE_PROCESSES

                                      Archive Log

CONTENT COPY OF REDO LOG FILES.

LOG_ARCHIVE_DEST

$ORACLE_HOME/dbs/arch

SQL>archive log list

SQL>select log_mode from v$database;

How to enable archive log:

SQL>shutdown immediate

Specify archive destination in pfile

log_archive_dest=/disk3/oradata/earnest3/arch

$mkdir -p /disk3/oradata/earnest3/arch

SQL>startup mount

SQL>alter database archivelog;

SQL>alter database open;

ENABLING ARCHIVE LOG MODE

SQL>archive log list

SQL>select log_mode from v$database;

SQL>shutdown immediate

SQL>exit

$cd $ORACLE_HOME/dbs

dbs]$vi init$ORACLE_SID.ora163 line

log_archive_dest=/disk3/oradata/earnest3/arch

dbs]$cd /disk3/oradata/earnest3

$mkdir arch

SQL>startup mount

SQL>archive log list

SQL>alter database archivelog;

SQL>archive log list

SQL>alter database noarchivelog;

SQL>alter database archivelog;

SQL>alter database open;

$cd /disk3/oradata/earnest3/arch

$ls -l

SQL>alter system switch logfile;