At thread width, the debugging commands apply only to the TOI, the thread that has the focus, plus any threads that belong to its lockstep group, if one exists. NextGen TotalView for HPC does not allow other program threads to run, but manager threads run freely.

Debugging commands selected from the Thread menu also run at thread width.

Operating on a thread isn’t the same as operating on a thread’s process, because a process can have more than one thread.

Thread-level single-step operations can fail to complete if the TOI needs to synchronize with a thread that isn’t running. For example, if the TOI requires a lock that another held thread owns, and steps over a call that tries to acquire the lock, the primary thread can’t continue successfully. You must allow the other thread to run in order to release the lock. In this case, you should use process-width stepping instead.