InnoDB Standard Monitor and Lock Monitor Output For a description of each metric reported by the Standard Monitor, refer to the Metrics chapter in the Oracle Enterprise Manager for MySQL Database User’s Guide. This section shows the timestamp, the monitor name, and the number of seconds that per-second averages are based on. The number of seconds is the elapsed time between the current time and the last time  InnoDB  Monitor output was printed. The  srv_master_thread  lines shows work done by the main background thread. This section reports threads waiting for a semaphore and statistics on how many times threads have needed a spin or a wait on a mutex or a rw-lock semaphore. A large number of threads waiting for semaphores may be a result of disk I/O, or contention problems inside  InnoDB . Contention can be due to heavy parallelism of queries or problems in operating system thread scheduling. Setting the innodb_thread_concurrency  system variable smaller than the default value might help in such situations. The  Spin rounds per wait  line shows the number of spinlock rounds per OS wait for a mutex. Mutex metrics are reported by  SHOW ENGINE INNODB MUTEX . This section provides information about the most recent foreign key constraint error. It is not present if no such error has occurred. The contents include the statement that failed as well as information about the constraint that failed and the referenced and referencing tables. This section provides information about the most recent deadlock. It is not present if no deadlock has occurred. The contents show which transactions are involved, the statement each was attempting to execute, the locks they have and need, and which transaction  InnoDB  decided to roll back to break the deadlock. The lock modes reported in this section are explained in Section 15.7.1, “InnoDB Locking” . If this section reports lock waits, your applications might have lock contention. The output can also help to trace the reasons for transaction deadlocks. This section provides information about threads that  InnoDB  uses to perform various types of I/O. The first few of these are dedicated to general  InnoDB  processing. The contents also display information for pending I/O operations and statistics for I/O performance. The number of these threads are controlled by the  innodb_read_io_threads  and innodb_write_io_threads  parameters. See Section 15.14, “InnoDB Startup Options and System Variables” . This section shows the status of the  InnoDB  insert buffer (also referred to as the change buffer) and the adaptive hash index. • INSERT BUFFER AND ADAPTIVE HASH INDEX • FILE I/O • TRANSACTIONS • LATEST DETECTED DEADLOCK • LATEST FOREIGN KEY ERROR • SEMAPHORES • BACKGROUND THREAD • Status 3345