The “niceness” of a process is a numeric hint to the kernel about how the process should be treated in relation to other processes contending for the CPU. The strange name is derived from the fact that it determines how nice you are going to be to other users of the system. A high nice value means a low priority for your process: you are going to be nice. A low or negative value means high priority: you are not very nice. The range of allowable niceness values is -20 to +19.
-20 –> highest priority
+19 –> lowest priority
How to renice a process sy the PID is 1267
renice +19 1267
The above command will change the priority to +19 (least) from the existing priority