Hi Murtaza,
Is the problem with the cron utility it self or problem with the script in the cronjob.
Means, is the job triggered at all by cron or when it is triggered, it fails ?
Can you share the command you are using. How about setting up a DBACOCKPIT. You can schedule backups from their as well.
If your SAP system is on Maxdb, you can schedule backups in dbacockpit or if you have a central system like solman from where you want to monitor and setup dbacocpit manually, check these
DBACOCKPIT and Solman Monitoring for MaxDB Database : How to Setup -I
DBACOCKPIT and Solman Monitoring for MaxDB Database : How to Setup -II
Thanks
Amit