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Hot Backup in Oracle
Basic procedure for a hot backup
The following pseudo code(!) demonstrates how a hot backup is taken on Oracle.
for ts in tablespaces alter tablespace $ts begin backup for df in datafiles of $ts cp $df $SAVE/$df alter database datafile '$df' end backup end alter tablespace end backup end alter system switch logfile alter database backup controlfile to trace
The second last step (alter system switch logfile) forces a checkpoint which in turn updates the datafile headers with a new SCN that is the same for all datafile headers.
Note: Online redo log files should never be backed up!
Differences while hot backup and normal db operation
If the database is hot backuped, the operation is different from normal db operation in only two ways: