I have three users on my server
a) root
b) oracle
c) download

i want to take backup of cron for everyuser everyday. Is there any way to schedule this process.

NAME

crontab

-- maintain crontab files for individual users (V3)

SYNOPSIS

crontab

[-u user] file
crontab [-u user] { -l | -r | -e }

... Did you try crontab(1)?

Have you thought of scheduling a cron job for this?

you can edit crontab file >(crontab -e) command...but if you want to take oracle backup you must stop oracle after start backup...are your backup ufsdump backup???

I think that the OP wants to backup the crontab files for every user every day. This would be as simple as doing a 'cp -p' of the crontab files. Use the following script:

today=$(date +%Y%m%d)
mkdir /some_backup_dir/$today
cp -p /var/spool/cron/crontabs/* /some_backup_dir/$today