In this session will learn, how to fix ORA-00265: instance recovery required

SQL> alter database archivelog;
alter database archivelog
*
ERROR at line 1:
ORA-00265: instance recovery required, cannot set ARCHIVELOG mode

Cause:

The database was crashed itself or you issued shutdown abort or startup force commands.

In my case I issued the following command, to take database into mount state.

SQL> startup mount force;

Solution :

Open the database and shutdown immediate then mount it to keep in archive log mode and open.

1. alter database open;

2. shutdown immediate

3. startup mount

4. alter database archivelog;

5. alter database open;