A task is an executable that is internal to SAP ASE (for example, user connections, daemons such as the housekeeper task, and kernel tasks such as I/O handling).
User tasks – represent user connections and are capable of executing user queries. An isql connection is an example of a user task.
Service tasks – not associated with specific users, and do not issue user queries. Service tasks include the housekeeper tasks, checkpoints, replication agent threads, and so on).
System tasks – kernel-level versions of service tasks. System tasks include I/O handlers, the clock handler, cluster membership service, IP link monitor, and so on.
SAP ASE multiplexes tasks across the threads. Run-to-completion (RTC) thread pools place a task in a thread pool and the next available thread picks up the task, which remains on the thread until it completes, and terminates when it finishes running.
See Performance and Tuning Series: Basics > Base Priority for a description of setting the task priority for an individual task.
The monTask monitoring table includes a row for each task running on SAP ASE. See the Reference Manual: Tables.