what is mean by Re-KYC via CKYCR?

[panu24]

My Father received sms from HDFC bank
Re-KYC due:
Update your KYC for HDFC Bank Cust ID
xxxx via CKYCR documents as per the
RBI guidelines.

What does this mean? Can KYC be done by him online?

 

[Lynx]

And my brother recieved same Re-KYC due message from Indian bank.