Database Size versus Backup Size

Question

Is there a formuly I can use, to calculate the amount of backup space I will need ?
We have a backup script, for backing up to disk - I copy and paste the main body of the script below. My would like to be able to estimate how much backup space we need, as the database grows.
connect target
run
change archivelog all crosscheck;
backup database
include current controlfile
format '/backup/rman/oraadmin/DBF_%d_%p_%s.RMan'
filesperset 4
tag = 'Full_DB_Backup';
sql 'ALTER SYSTEM ARCHIVE LOG CURRENT';
run
# Backup Archived Logs
backup archivelog all
format '/backup/rman/oraadmin/ARC_%d_%p_%s.RMan'
filesperset 16
delete input;
run
#* Copy Current Control File to Backup Location
copy current controlfile to '/backup/rman/oraadmin/ControlFile.Ctl';
}

Answer 1

use this script -
column dummy noprint
column pct_used format 999.9 heading "%|Used"
column name format a16 heading "Tablespace Name"
column Kbytes format 999,999,999 heading "KBytes"
column used format 999,999,999 heading "Used"
column free format 999,999,999 heading "Free"
column largest format 999,999,999 heading "Largest"
break on report
compute sum of kbytes on report
compute sum of free on report
compute sum of used on report
select nvl(b.tablespace_name,
nvl(a.tablespace_name,'UNKOWN')) name,
kbytes_alloc kbytes,
kbytes_alloc-nvl(kbytes_free,0) used,
nvl(kbytes_free,0) free,
((kbytes_alloc-nvl(kbytes_free,0))/
kbytes_alloc)*100 pct_used,
nvl(largest,0) largest
from ( select sum(bytes)/1024 Kbytes_free,
max(bytes)/1024 largest,
tablespace_name
from sys.dba_free_space
group by tablespace_name ) a,
( select sum(bytes)/1024 Kbytes_alloc,
tablespace_name
from sys.dba_data_files
group by tablespace_name
UNION
select sum(bytes)/1024 kbytes_alloc, tablespace_name
from sys.dba_temp_files
group by tablespace_name )b
where a.tablespace_name (+) = b.tablespace_name;
Message was edited by:
jittu13