Updating antivirus definition without restarting…

Does anyone of you know which Anti Virus software that doesn’t require the system to restart when updating its antivirus definition?

Because I have a server which runs 24 hours and it doesn’t have time to restart, because the operation is also runs 24 hours without down time..
And I feel that it’s pretty anoying when I have to restart the server just because I need to update the antivirus definition…

Again…
Does anyone of you know which Anti Virus software that doesn’t require the system to restart when updating its antivirus definition?

Thank you for your time and answers…