Difference between Nzstop vs Nzsystem stop

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IBM Netezza
  Nzstop       nzsystem stop      nzsystem stop -now   
Stops Netezza immediately by killing the queries that are running currently. This is the recommended   command to stop Netezza.
NOTE: You can run   nzstart/nzstop directly on server only. You cannot issue these commands from   a client machine.   
Waits for the   current active queries to complete before stopping. All the queued and new   requests are killed.   
Similar to nzstop,   this command also stops Netezza immediately by killing the currently running   queries.
NOTE: when you use   “-now” with any state like pause, offline, restart, and stop system will   abort all the running transactions and will immediately change to that state.