Online hot backup

Using OS Level copy command to backup oracle database
1. Make sure database in archive log mode.
SQL> archive log list
Database log mode Archive Mode
Automatic archival Enabled
Archive destination /ora/ora920/archlog/PROD
Oldest online log sequence 41288
Next log sequence to archive 41294
Current log sequence 41294
SQL>

If not archive log mode , modify init parameter file , add following parameter
log_archive_start = true
log_archive_dest_1 = "location=/ora/ora920/archlog/PROD"
log_archive_format = PROD_%t_%s.arc

2. Bring tablespace one by one to backup mode(Exclude temp tablespace).
alter tablespace xxx begin backup;

or
bring whole database to backup mode.
alter database begin backup;

3. Copy all datafile to backup disk.

4. Bring tablespace one by one to end-backup(Exclude temp tablespace).
alter tablespace xxx end backup;

or
bring whole database to end-backup mode.
alter database end backup;

5. Generating after end backup redo log.
alter system archive log current;
or
alter system switch logfile;

6. Copy all archived logs that generated during backup period to backup disk.