No large data processing system or subsystem can continually operate independently of system programmer or operator intervention. A two-way communication mechanism between the operator and JES2 is required. Based on system workload and device requirements, JES2 must communicate its status to the operator, system programmer, or both. JES2 issues messages to communicate job and device status, problem situations, system resource constraint situations, and performance status. Through commands, you can request current status and through the use of various tools you can obtain further information to diagnose and correct problem and system failure situations. Interacting with JES2 provides an overview of these topics.