InnoDB Configuration Note 15.8 InnoDB Configuration 15.8.1 InnoDB Startup Configuration 3102 •Specifying Options in a MySQL Option File •Viewing InnoDB Initialization Information •Important Storage Considerations •System Tablespace Data File Configuration •InnoDB Doublewrite Buffer File Configuration • lock_schedule_refreshes • lock_rec_grant_attempts • lock_rec_release_attempts Prior to MySQL 8.0.20,  InnoDB  also uses a First In First Out (FIFO) algorithm to schedule transactions, and the CATS algorithm is used under heavy lock contention only. CATS algorithm enhancements in MySQL 8.0.20 rendered the FIFO algorithm redundant, permitting its removal. Transaction scheduling previously performed by the FIFO algorithm is performed by the CATS algorithm as of MySQL 8.0.20. In some cases, this change may affect the order in which transactions are granted locks. You can view transaction scheduling weights by querying the  TRX_SCHEDULE_WEIGHT  column in the INFORMATION_SCHEMA.INNODB_TRX  table. Weights are computed for waiting transactions only. Waiting transactions are those in a  LOCK WAIT  transaction execution state, as reported by the  TRX_STATE column. A transaction that is not waiting for a lock reports a NULL  TRX_SCHEDULE_WEIGHT  value. INNODB_METRICS  counters are provided for monitoring of code-level transaction scheduling events. For information about using  INNODB_METRICS  counters, see Section 15.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table” . The number of attempts to release record locks. A single attempt may lead to zero or more record locks being released, as there may be zero or more record locks in a single structure. The number of attempts to grant record locks. A single attempt may result in zero or more record locks being granted. The number of times the wait-for graph was analyzed to update the scheduled transaction weights. This section provides configuration information and procedures for  InnoDB  initialization, startup, and various components and features of the  InnoDB  storage engine. For information about optimizing database operations for  InnoDB  tables, see Section 8.5, “Optimizing for InnoDB Tables” . The first decisions to make about  InnoDB  configuration involve the configuration of data files, log files, page size, and memory buffers, which should be configured before initializing  InnoDB . Modifying the configuration after  InnoDB  is initialized may involve non-trivial procedures. This section provides information about specifying  InnoDB  settings in a configuration file, viewing  InnoDB initialization information, and important storage considerations.