WINCC 7.3 SERVER ARCHIVE PROBLEM ON CLIENTS

In my Plant I am having Two Redundant WinCC 7.3 Server with Server 2012 OS and 6 Clients.Earlier system works fine but since last one month we observed one strange problem of Archive:-

Both Servers Server-1(Master),Server-2(Redundant) and All 6 Clients on Runtime will work fine all Clients connected to Master Server-1.

If we deactivate Server-1(Master) all clients switchover to Server-2(Redundant),now if again Activate Server-1(Master) all clients switchover to Server-1.

If we deactivate Server-2(Redundant) all clients remain connected to Server-1(Master) but on all clients there is no archive data available and on Alarm/Events screen message appears "No connection to data server". While on Server-1(Master) all archive data works fine. If we again activate Server-2(Redundant) server archive data available on all clients.

Please provide solution to this problem  

Thanks for your reply, but in my situation if on client side on "Configuration Standard Server" setting if we set "No Standard Server " to all options and in "Configure the Server Data" setting if we set "No Preferred Server" at "Preferred Server Option" client will work fine until Redundant Server Activate again.

When Server-2(Redundant Server) activate again  "No data connection to Server " shown on client and again we have to restore above setting as on "Configuration Standard Server" setting if we set "Server-1(Main Server) " to all options and in "Configure the Server Data" setting if we set "Server-1(Main Server)" at "Preferred Server Option" client will work fine.