About quiescing the database application
Most database applications are transactionally consistent only at particular points in time. Sometimes, they are consistent only after they have been shut down. Since many database applications must be available constantly, many applications can reach transactional consistency at regular intervals or in response to an external event. This process is called application quiesce, described in this section.
In database application quiesce, an external signal or message is sent to a receptive database. In response, the database finishes the current transaction or group of transactions and tells the snapshot consumer when the transactions are complete. The database then waits for the indication that normal operations can resume. After the database indicates that it has reached a state of transactional consistency, the final steps of creating the snapshot can proceed.
Once the snapshot has been created, another signal is sent to the waiting database to resume normal operations. This procedure is called unquiescing the application.
