If you are running services and P6 on the same server, you should keep the defaults. If you have leveling work that needs to be done immediately, you should set the Interval low (e.g., 10s) and the Concurrent Threads high (e.g., 20). Remember that if the server is actively doing leveling work, all users will experience delays in the application.
To set your leveler settings:
Open the Primavera P6 Administrator.
In the Configurations tab, expand your configuration.
Expand Services/Leveler.
In the Interval field, enter the amount of time the Web Leveler will wait before leveling the next available job (in 1d1h1m1s format - specifying only numbers without letters implies milliseconds).
The default is 10s.
Enter anything from 1s-24d20h31m23s647.
In the Concurrent Threads field, enter the number of processes (active levelers) used for leveling on this server. A value of 0 indicates this server will not perform leveling.
The default is 2.
Enter anything from 0-20.
In the Active Mode field, choose true if you want jobs processed continuously until all jobs are leveled. Choose false if you want each job processed according to the Leveling Interval.