Allow oracle operating system user to schedule jobs on Linux / Unix

As the root user, add oracle to the /etc/cron.allow file with the echo command:

echo oracle >> /etc/cron.allow

Once the oracle entry is added to the /etc/cron.allow file, the os user oracle can use the crontab utility
to schedule a job

The root user can always schedule jobs with the crontab utility. Other users must be listed in
the /etc/cron.allow file. If the /etc/cron.allow file does not exist, then the operating system
user must not appear in the /etc/cron.deny file. If neither the /etc/cron.allow nor the /etc/
cron.deny file exists, then only the root user can access the crontab utility.