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The maximum number of tables for which the Performance Schema maintains lock statistics. If this maximum is exceeded such that table lock statistics are lost, the Performance Schema increments the Performance_schema_table_lock_stat_lost  status variable. 

• performance_schema_max_thread_classes 

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The maximum number of thread instruments. For information about how to set and use this variable, see Section 27.7, “Performance Schema Status Monitoring” . 

• performance_schema_max_thread_instances 

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The maximum number of instrumented thread objects. The value controls the size of the threads  table. 

If this maximum is exceeded such that a thread cannot be instrumented, the Performance Schema increments the Performance_schema_thread_instances_lost  status variable. For information about how to set and use this variable, see Section 27.7, “Performance Schema Status Monitoring” . 

The max_connections  system variable affects how many threads can run in the server. 

performance_schema_max_thread_instances  affects how many of these running threads can be instrumented. 

The variables_by_thread  and status_by_thread  tables contain system and status variable information only about foreground threads. If not all threads are instrumented by the Performance Schema, this table misses some rows. In this case, the Performance_schema_thread_instances_lost  status variable is greater than zero. 

