Performance Schema Instance Tables • cond_instances : Condition synchronization object instances • file_instances : File instances • mutex_instances : Mutex synchronization object instances • rwlock_instances : Lock synchronization object instances • socket_instances : Active connection instances These tables list instrumented synchronization objects, files, and connections. There are three types of synchronization objects:  cond ,  mutex , and  rwlock . Each instance table has an  EVENT_NAME  or NAME  column to indicate the instrument associated with each row. Instrument names may have multiple parts and form a hierarchy, as discussed in Section 27.6, “Performance Schema Instrument Naming Conventions” . The  mutex_instances.LOCKED_BY_THREAD_ID  and rwlock_instances.WRITE_LOCKED_BY_THREAD_ID  columns are extremely important for investigating performance bottlenecks or deadlocks. For examples of how to use them for this purpose, see Section 27.19, “Using the Performance Schema to Diagnose Problems” The  cond_instances  table lists all the conditions seen by the Performance Schema while the server executes. A condition is a synchronization mechanism used in the code to signal that a specific event has happened, so that a thread waiting for this condition can resume work. When a thread is waiting for something to happen, the condition name is an indication of what the thread is waiting for, but there is no immediate way to tell which other thread, or threads, causes the condition to happen. The  cond_instances  table has these columns: 27.12.3.1 The cond_instances Table The instrument name associated with the condition. The address in memory of the instrumented condition. TRUNCATE TABLE  is not permitted for the  cond_instances  table. The  file_instances  table lists all the files seen by the Performance Schema when executing file I/O instrumentation. If a file on disk has never been opened, it is not shown in  file_instances . When a file is deleted from the disk, it is also removed from the  file_instances  table. The  file_instances  table has these columns: • FILE_NAME •Index on ( NAME ) •Primary key on ( OBJECT_INSTANCE_BEGIN ) • OBJECT_INSTANCE_BEGIN • NAME The  cond_instances  table has these indexes: 27.12.3.2 The file_instances Table 4953