4.6. Hangs and loops
One of the difficult things to determine is whether a system or subsystem is in a hung or looping state. While the symptoms in many cases are similar — for example, the inability to process other units of work, or transactions, or the inability to get the system or subsystem to accept commands — the key difference is whether there is CPU and EXCP activity that indicates the system is still performing work.
If no other tasks can be dispatched within a subsystem, and the CPU activity is high, often 100 percent, this is generally a symptom that we have a loop condition. Loops can usually be categorized as either enabled, disabled or spin loops.
Loops are caused by a program, application, or subsystem attempting to execute the ...
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