The NXT node uses a Java mechanism called "Shutdown Hook" to close the database and perform necessary cleanup before shutting down the Java process.
Killing the Java process without letting the shutdown hook execute may result in database corruption.
Therefore, when shutting down the NXT node, always use one of the following methods:
1. On GUI environment, use the "Shutdown" menu item from the system tray icon.
2. From the command line use the kill <pid>
command.
If possible, never use the following methods for shutting down the node:
kill -9 <pid>
or kill the process from the Windows task manager or using Mac OS/X similar function.