The "nice" command in Unix-like operating systems is used to change the priority of a process, including Oracle database processes, when it is started. The nice value determines the priority of the process, with a higher nice value indicating a lower priority.
In Oracle, the nice value of a process can be used to adjust its dispatch priority and determine the amount of CPU cycles that it receives. By default, Oracle processes are started with a nice value of 0, which indicates a normal priority. If a process is started with a higher nice value, it will receive a lower priority and a smaller share of the CPU cycles.
Here is an example of how to start an Oracle process with a higher nice value using the "nice" command:
$ nice -n 10 sqlplus / as sysdba
In this example, the -n 10 option sets the nice value to 10, which gives the process a lower priority. The sqlplus command is used to start an instance of the SQL*Plus command-line interface, and the / as sysdba options are used to connect to the database as the system administrator.
Note that changing the nice value of an Oracle process only affects its dispatch priority, not the amount of CPU cycles that are available to the system as a whole. If the system is under heavy load, processes with lower priorities may still be subject to performance issues, even if they have been started with a higher nice value.
In general, the use of the "nice" command to adjust the dispatch priority of an Oracle process should be done with caution, and only after careful consideration of the potential impact on the performance of the system as a whole.