Hi everybody,
can anybody tell me how do i take an online backup.If possible pls provide me the step by step procedure.
Right now what i am doing is following the steps given below

1.Execute archive log list from Server Manager. Note value for "Oldest online log sequence." This is the oldest redo log required for using the online backup.

2.Execute alter tablespace name begin backup from Server Manager. This step prepares the tablespace for online backup by freezing the headers in the datafiles for the tablespace.

But the prob is when i issue the above command it is giving me the error
ORA-01123:cannot start online backup;media recovery not enabled.

Then i enabled the follo in init.ora file
log_archive_start = true
log_archive_dest = c:\orant\database\pras
log_archive_format = "%ORACLE_SID%%S.%T"

Still it is giving me the same error i also tried
alter database archivelog;

pls help,thanking u all in advance..

pras