Hi
>> when we run full backup, my system performance comes to an halt
First, this is normal, as RMAN does full-table scans against all of the tables, depending on the backup type.
Also, this MUST be a hot backup, since the database is running.
Have you considered trying incremental backups?
Please read:
http://www.dba-oracle.com/t_incr_different...ive_backups.htm*********************************************
>> RMAN backup & recovery I/O
Your disk channels are saturated!
The ONLY way to fix this issue is to improve the speed of the I/O subsystem (i.e. more disks or faster disks), or do the backups during scheduled downtime, or do incremental backups . . . .
Another solution is to move to SSD:
http://www.dba-oracle.com/oracle_tips_SSD.htm