A common problem is that when two AM instances are both running, you see the number of session requests exceeds the number of logins. For example, the test output may look similar to this:
4075 40750 358600 4167 41670 400032 19945 199450 1913866 3979 39790 381984 0 0 0 3033 30330 297234 3946 39460 359086 39194 391891 3713840 a
Note that for each login request, there are now 5 session requests, and 0.75 notifications. The total number of requests do add up though. This indicates there are no other unexpected requests. There more session requests per login because the sticky load balancing is not working properly. A user logged in on one Access Manager instance is sometimes sent to another Access Manager instance for session validation and logout. The second Access Manager instance must generate extra session and notification requests to the originating Access Manager instance to perform the request. The extra requests increase the system workload and reduce the maximum throughput the system can provide. In this case, the two Access Manager instances cannot double the throughout of the single AM throughput. You can address the problem by reconfiguring the load balancer. The problem should have been caught during modular verification steps in the system construction phase.