Back in 2003 when Oracle 10g was released and bigfile tablespaces were first introduced, not many databases were in the terabyte or petabyte weight-class. The very feature of having your data warehouse downsized in the number of files through the use of bigfile tablespaces, was not considered very useful unless you would use Automatic Storage Management (ASM).
But those who believed that having a tablespace terabyte sized, in a single datafile, crashed their belief in the moment of having to do a backup. Why? Because in Oracle 10g you couldn’t do the backup in parallel of a single datafile. Better said: you couldn’t use the RMAN multi-channelling feature because a single datafile had to go through the same pipe in the whole backup process.
It’s typical in the technology arena to create new features that create new needs, that will be solved and made easier, through the introduction of, yet, new features. So in that same line of thought, Oracle 11g introduced the capability of doing a RMAN multi-channelling, hence parallel, backup of a single datafile, by slicing and dicing it into smaller chunks.
How can we do that? It’s simple: add the following clause to the RMAN command “BACKUP”:
SECTION SIZE <size in bytes>
To give you some examples for the see-it-to-believe-it folks why not give some URLs from the hard-working bloggers (not lazy like me!):
If you want to Google it, try: “Multi-section backups”. You’ll speed up the time it takes to backup your huge datafiles in your even bigger database.
Hope it helped some one out there.