how to create a log file if lost? 1-Now you are facing a problem that the db doesn't open
2-log on the db as sys dba
run>cmd>sqlplus username/password as sysdba
3-alter database clear logfile group (number of the lost group file);
such as
alter database clear logfile group 2;
4- open the database
alter database open;
How to Set the DB on the archive log mode ? 1- log on the db (database) as sys dba
>sqlplus >username/password as sysdba
2- shutdown the DB immediate
>sqlplus shutdown immediate
3-start db in mount state
>sqlplus startup mount
4-alter database archive log
5-alter database open
