I use systemrescue cd linux distribution, it has clamav inbuilt to scan for windows viruses ,when updating the virus database manually, is it sufficient to download and replace daily.cvd, or should i download mail.cvd?

also i saw virus update files in clamav.com https://www.clamav.net/download/cvd , both the definitions are same?

If you are using Clam Antivirus, we can't help you here. These forums are for the ClamWin antivirus program, which is a Windows port of the Clam AV program.

Regards,

daily is daily virus sigdefinition file, they are the last updated signatures (updated many times per day), main it's the main db, it's big and contains consolidated signatures this avoid downloading 15mb or more of signature each update