Backup Set:
A standard RMAN backup set contains one or
more backup pieces, and each of these pieces consists of the data blocks for a
particular datafile stored in a special compressed format. When a datafile
needs to be restored, therefore, the entire datafile essentially needs to be
recreated from the blocks present in the backup piece.
Image Copy:
An image copy of a datafile, on the other hand, is
much faster to restore because the physical structure of the datafile already
exists. Oracle 10g now permit image copies to be created at the database,
tablespace, or datafile level through the new RMAN directive BACKUP AS
COPY. For example, here is a command script to create image copies for all
datafiles in the entire database:
RUN {
# Set the
default channel configuration. Note the use of the
# %U directive
to insure unique file names for the image copies
ALLOCATE
CHANNEL dbkp1 DEVICE TYPE DISK FORMAT 'D:\oracle\rman\ora10G\U%';
# Create an
image copy of all datafiles in the database
BACKUP AS COPY
DATABASE;
}
why dont the client wants to have backupsets
rather
than image
copies? I know that Oracle first perfers to the image copies
compare to
incremental or backupsets.
But, you
know, image copy is just a block to block copy, no compression. It
would take
good considerable time to finish the backup.
10g RMAN has
very rich features, like BTC, binary compression and etc.
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