Tuesday, November 11, 2008  What Happens during a hot backup?
There are a couple of myths around the hot backup or online
backup process:  Myth #1: The hot backup generates "a lot" of
redo information Myth #2: The archivelog mode "dramatically
slows down" the database Myth #3: When a hot backup is in
progress the target datafile is frozen.  There are two ways to
generate a hot backup, the first one is by a user managed backup
and the second one with recovery manager. The database is
required to be in archivelog mode for it to be able to perform
an online backup. Both ways to perform an online backup work in
a similar way, as I will further explain later, rman is more
efficient than the user managed backup.  User managed backup
alter tablespace ts_name begin backup;  When the command is
issued, at this point in time a checkpoint is performed against
the target tablespace; then the datafile header is frozen, so no
more updates are allowed on it (the datafile header), this is
for the database to know which was