If you want to roll forward an Oracle DB from a snapshot using future archives, then you need to put the database in backup mode before taking a snapshot.  If you want to use the Oracle DB from a snapshot as is, then you don't need to to put the database in backup mode.

 

Sample PL/SQL script to put the DB in backup mode before taking a snapshot:

su - oracle << EOF

sqlplus "/as sysdba" <<END

whenever sqlerror exit1

alter system archive log current;

alter database begin backup;

END

EOF

 

Sample PL/SQL script to take the DB out of backup mode after taking a snapshot:

su - oracle << EOF

sqlplus "/as sysdba" <<END

whenever sqlerror exit1

alter database end backup;

alter system archive log current;

END

EOF