When accessing the lock table, the local mutex is acquired first and only then the shared mutex is acquired. If all the connections belong to the single address space (SS and SC architectures), all the contention is on the local mutex, not on the shared mutex. But the local mutex "blocks" are not encounted in the statistics, hence both "acquire blocks" and "mutex wait" counters will be always zero in this case, making it hard to analyze the possible performance bottlenecks (this is mostly true for SC, as SS is almost never LM bound).