If the connection from the application server to the data server encounters problems, the application server ECP connection enters the Trouble state. In this state, application server ECP daemons exist and are actively try to restore the connection. An underlying TCP connection may or may not still exist. The recovery method is similar whether or not the underlying TCP connection gets reset and must be recreated, or if it stops working temporarily.
During the application server Time to wait for recovery timeout (default of 20 minutes), the application server attempts to reconnect to the data server to perform ECP connection recovery. During this interval, existing network requests are preserved, but the originating application server-side user process blocks new network requests, waiting for the connection to resume. If the connection returns within the Time to wait for recovery timeout, it returns to the Normal state and the blocked network requests proceed.
For example, if a data server goes offline, any application server connected to it has its state set to Trouble until the data server becomes available. If the problem is corrected gracefully, a connection’s state reverts to Normal; otherwise, if the trouble state is not recovered, it reverts to Not Connected.
Applications continue running until they require network access. All locally cached data is available to the application while the server is not responding.