Always On - How to update SQL server in this configuration.

Hello,

We have two SQL servers for our SharePoint farm: they are in the 2012 SP2 release and we want to upgrade to 2012 SP4.

Is it possible to update one by one with the "always on" a mechanism without impact? We are concerned that with two SQL Server servers in a different version of the software, synchronization alters the data?

Thank you in advance for your help,

Have a good day,
Clement