Enabling archivelog mode

SQL> SELECT LOG_MODE FROM SYS.V$DATABASE;

LOG_MODE
------------
NOARCHIVELOG

show parameter archive 

will tell u the archive destination etc ... 

so , create spfile from pfile incase of the db running onthe pfile means, then shutdown startup mount and follow the steps

SQL> startup mount
ORACLE instance started.

Total System Global Area  184549376 bytes
Fixed Size                  1300928 bytes
Variable Size             157820480 bytes
Database Buffers           25165824 bytes
Redo Buffers                 262144 bytes
Database mounted.

SQL> alter database archivelog;
Database altered.

SQL> alter database open;
Database altered.

ou can see here that we put the database in ARCHIVELOG mode
by using the SQL statement "alter database archivelog", but 
Oracle won't let us do this unless the instance is mounted but
not open.  To make the change we shutdown the instance, and then
startup the instance again but this time with the "mount" option
which will mount the instance but not open it.  Then we can
enable ARCHIVELOG mode and open the database fully with the "alter
database open" statement.

There are several system views that can provide us with information reguarding archives, such as:

V$DATABASE

Identifies whether the database is in ARCHIVELOG or NOARCHIVELOG mode and whether MANUAL (archiving mode) has been specified.

V$ARCHIVED_LOG

Displays historical archived log information from the control file. If you use a recovery catalog, the RC_ARCHIVED_LOG view contains similar information.

V$ARCHIVE_DEST

Describes the current instance, all archive destinations, and the current value, mode, and status of these destinations.

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, the RC_BACKUP_REDOLOG contains similar information.

V$LOG

Displays all redo log groups for the database and indicates which need to be archived.

V$LOG_HISTORY

Contains log history information such as which logs have been archived and the SCN range for each archived log.

Using these tables we can verify that we are infact in ARCHIVELOG mode:
SQL> select log_mode from v$database; LOG_MODE ------------ ARCHIVELOG SQL> select DEST_NAME,STATUS,DESTINATION from V$ARCHIVE_DEST;