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    Friday, May 29, 2020

    Archivelog Mode and noarchivelog mode in Oracle database and How to convert from noarchivelog mode to archivelog mode

    ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. 

    NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time.

    Converting database from noarchivelog mode to archivelog mode:

    ---> Please note that converition of noarchivelog to archivelog mode is only posible in database mount state:

    1. Login to database and verify the database state and log mode:

    sqlplus / as sysdba

    SQL> select name, open_mode, database_role, log_mode from v$database;

    NAME      OPEN_MODE            DATABASE_ROLE    LOG_MODE
    --------- -------------------- ---------------- ------------
    DEVDB     READ WRITE           PRIMARY          NOARCHIVELOG

    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           5
    SQL> 

    2. Shutdown the database

    SQL> shut immediate 
    Database closed.
    Database dismounted.
    ORACLE instance shut down.

    3. Start the database in mount mode.
     
    SQL> startup mount;
    ORACLE instance started.

    Total System Global Area 1570009088 bytes
    Fixed Size                  2253584 bytes
    Variable Size             973081840 bytes
    Database Buffers          587202560 bytes
    Redo Buffers                7471104 bytes
    Database mounted.

    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           5
    SQL> 

    4. Convert the database from noarchivelog to archivelog mode 

    SQL> alter database archivelog;

    Database altered.

    5. Open the database 

    SQL> alter database open;

    Database altered.

    6. Verify the database state and log mode:
     
    SQL> select name, open_mode, database_role, log_mode from v$database;

    NAME      OPEN_MODE            DATABASE_ROLE    LOG_MODE
    --------- -------------------- ---------------- ------------
    DEVDB     READ WRITE           PRIMARY          ARCHIVELOG

    SQL> archive log list 
    Database log mode              Archive Mode
    Automatic archival             Enabled
    Archive destination            USE_DB_RECOVERY_FILE_DEST
    Oldest online log sequence     3
    Next log sequence to archive   5
    Current log sequence           5
    SQL> 

    Converting database from archivelog mode to noarchivelog mode:

    ---> Please note that converition of noarchivelog to archivelog mode is only posible in database mount state:

    1. Login to database and verify the database state and log mode:

    SQL> select name, open_mode, database_role, log_mode from v$database;

    NAME      OPEN_MODE            DATABASE_ROLE    LOG_MODE
    --------- -------------------- ---------------- ------------
    DEVDB     READ WRITE           PRIMARY          ARCHIVELOG

    SQL> archive log list 
    Database log mode              Archive Mode
    Automatic archival             Enabled
    Archive destination            USE_DB_RECOVERY_FILE_DEST
    Oldest online log sequence     3
    Next log sequence to archive   5
    Current log sequence           5
    SQL> 

    2. Shutdown the database

    SQL> shut immediate 
    Database closed.
    Database dismounted.
    ORACLE instance shut down.

    3. Start the database in mount mode.

    SQL> startup mount;
    ORACLE instance started.

    Total System Global Area 1570009088 bytes
    Fixed Size                  2253584 bytes
    Variable Size             973081840 bytes
    Database Buffers          587202560 bytes
    Redo Buffers                7471104 bytes
    Database mounted.

    4. Convert the database from archivelog to noarchivelog mode 

    SQL> alter database noarchivelog;

    Database altered.

    5. Open the database 

    SQL> alter database open; 

    Database altered.

    6. Verify the database state and log mode:

    SQL> select name, open_mode, database_role, log_mode from v$database;

    NAME      OPEN_MODE            DATABASE_ROLE    LOG_MODE
    --------- -------------------- ---------------- ------------
    DEVDB     READ WRITE           PRIMARY          NOARCHIVELOG

    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           5
    SQL> 


    Please follow more on my YouTube 
    https://youtu.be/PUYuv0aU5S0

    Regards,
    Mallik


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