We're running Policy Server with 2 ODBC instances of Session Stores,
when the first instance goes off line, then the connections are going
to the next Session Store, and when the first instance comes back
on-line, the connections doen't goes back to the first instance.
We want to know why ?
At first glance, the behavior is as expected. Even if the nomenclature
of the configuration suggest there's a loadbalancing, the following
configuration means failover, and not loadbalancing :
How to implement ODBC LoadBalancing for User Store
As such, the behavior you see is as expected and by design.