To stop a cluster engine, select the Database Cluster and choose Control => Stop or click the Stop Toolbar button.
When you use Control => Stop, an option dialog is presented where you can select the mode of database server shutdown to be used:
For more information on stop strategies, refer to pg_ctl in the PostgreSQL 7.3 Reference Manual.
The Stop Toolbar button always invokes the safer Smart database server shutdown mode.
The system updates the Status Bar at each step of the operation and refreshes the dialog when done.
With the Smart option, the backend waits for all transactions to finish. If there is a long-running transaction, the Control Center may timeout and believe that the stop operation has failed. However, the Smart stop request has already been sent to the backend and it will eventually stop. You need to correct the pending transaction problems and use the Refresh option after that to confirm that the database service has stopped.