1.How to check Log Mode:
SELECT LOG_MODE FROM V$DATABASE;

2.Change Log Mode:

Alter database archivelog; (Database must be in mounted mode, database Alter command will not permanently add entries in spfile, we need to do it manually)

to open database in mount only mode startup mount

3.Open database read only

ALTER DATABASE OPEN READ ONLY;

4. Open Database in read and write mode:

ALTER DATABASE OPEN READ WRITE;
However, read-write is the default mode.

5.Start commands

1.Normal start = startup
2.Startup mount


Other various commands

V$ARCHIVED_LOG

Displays historical archived log information from the control filL

Read Further: http://psadministrators.blogspot.com/2012/08/rman-commands.html