The user task is a task in the user kernel thread. It is responsible for processing SQL statements.
When a database session is opened, precisely one user task is given a fixed assignment to each client (in other words, to each user and each application program that is accessing the database instance).
The number of user tasks available is defined by the general database parameter MAXUSERTASKS. The general database parameter MAXCPU specifies the number of user kernel threads across which the user tasks are distributed. The user tasks generate the main load for the processor; other tasks, including the special threads, consume only a very small amount of processor time. You can use the parameter MAXCPU to restrict the number of processors that are used in parallel by the database instance.