Cold backup: shutdown the database and copy the datafiles with the help of

O.S. command. this is simply copying of datafiles just like any other text file

copy.

Holt backup: backup process starts even though database in running. The

process to take a hot backup is

1) sql> alter database begin backup;

2) copy the datafiles.

3) after copying

sql> alter database end backup;

Begin backup clause will generate the timestamp. it'll be used in backup

consistency i.e. when begin backup pressed, it'll generate the timestamp. During

restore, database will restore the data from backup till that timestamp and

remaining backup will be recovered from archive log.