Network outages such as system upgrades or hardware maintenance of servers are scheduled at regular intervals. During this time, you must disable the Citrix ADC load balancing services representing these servers,

You can perform a hard shutdown or graceful shutdown of a service. Hard shutdown disables a service immediately disrupting any established sessions and any transactions in progress, which may result in data loss. Hard shutdown changes the state of the service to DOWN.

Graceful shutdown disables a service after a wait time or after all the current active client connections are closed by either the server or the client. Graceful shutdown first changes the state of the service to Transition Out of Service (TROFS) state till the wait time is over or all the active connections are closed, after which the state changes to DOWN.

Often, however, you cannot estimate the amount of time needed for all the connections to a service to complete the existing transactions. If a transaction is unfinished when the wait time expires, shutting down the service may result in data loss. In this case, you can specify the graceful option, so that the service is disabled only when all the current active client connections are closed by either the server or the client. See the following table for behavior if you specify a wait time in addition to graceful option.

Persistence is maintained according to the specified method even if you enable graceful shutdown. The system continues to serve all the persistent clients, including new connections from the clients, unless the service is marked DOWN during the graceful shutdown state as a result of the checks made by a monitor.

The following table describes the functionality of graceful shutdown of a service for different combinations of graceful and wait time values.