Re: backup versus export of db

The third party is indeed correct and if an O/S tool is used outside of Oracle the backup is indeed worthless. But a hot backup can be done while these files are open. From within SQLDBA, issue the following:

     ALTER TABLESPACE tablespacename BEGIN BACKUP;
     Then use an O/S backup utilitly to backup all files belonging to 
       this tablespace.
     ALTER TABLESPACE tablespacename END BACKUP;

  Repeat for each tablespace.

Also you might want to get a copy of

      Rama Velpuri's
      Oracle:  Backup & Recovery Handbook, Oracle Press, 
      Osborne-McGraw-Hill