Take the 2-minute tour ×  We´re setting up RMAN to backup a
database over NFS and ZFS, for which I have to create shares and
mounting points (4 shares in my case).  I am trying to
anticipate the size of the shares, which should be the maximum
size of the backup. We´re going to proceed with an initial
backup level 0 and then we´ll do daily level 1 backups.  Is
there a mathematical formula for me to know the maximum backup
size at the end, using x as the database size?  Thank you,
share|improve this question  1 Answer 1  In short: Not really.
An RMAN backupset (e.g. BACKUP DATABASE) will backup up any
blocks in your datafiles that have never been used. This is
different from empty blocks. There's no way that I am aware of
to differentiate between blocks which are currently empty and
blocks which are unused.  From: http://docs.oracle.com/cd/B28359
_01/backup.111/b28270/rcmcncpt.htm#BRADV89481:  "RMAN always
skips blocks that have never been used"  If you were to do an
image copy (e.g. BACKUP AS COPY DATABASE),