1: Discontinuity: When programs are executed concurrently, they cooperate with each other because they share resources and complete the same task, resulting in the formation of a mutually restrictive relationship between these concurrently executed programs, leading to the appearance of program execution: execution-- Pause - execute
2: Loss of closure: when there are multiple concurrently executing programs in the system, each resource is shared by them, and the state of these resources is also changed by these programs, so the operating environment of a program will be affected by other programs .
3: Non-renewability