Problem was rectified by re matching RDC values with Hard drive.
Actually, there was another alarm, ""Data of RDC and hard Disk Inconsistent! Check robot data"
with this message drives alarm also there, and drives were not being operated neither on auto mode nor at manual.
But i am still unable to find the cause of data mismatching during operation.
either it is due to HDD.
or one thing can be possible, system motherboard in not origional (it is of old KUKA Computer.)
its own motherboard was faulty thats why old one available was used for it and it is working fine since last few months.