Transaction code SM51 description

Through this T-code SM51, we can know the the status of the particular Application server whether it is in active or inactive. This means we can get only one application server status.
To over come this we have another transaction code, that is SM66 T-CODE. From this we can know about all application servers status, those all are exist in one system.

RELEASE NOTE :
From T.code SM51, you can also able get RELEASE note of your current system. In that, kernel version, support package level, database release version, etc.