Replication and Binary Logging Options and Variables MURMUR32 XXHASH64 This system variable specifies the algorithm used to hash the writes extracted during a transaction. The default in MySQL 8.0 is that  transaction_write_set_extraction  is set to  XXHASH64 .  OFF  means that write sets are not collected.  transaction_write_set_extraction  is deprecated from MySQL 8.0.26, and will be removed in a future MySQL release. The  XXHASH64  setting is required for Group Replication, where the process of extracting the writes from a transaction is used for conflict detection and certification on all group members (see Section 18.3.1, “Group Replication Requirements” ). For a replication source server that has multithreaded replicas (replicas on which  slave_parallel_workers  is set to a value greater than 0), where  binlog_transaction_dependency_tracking  is set to  WRITESET or  WRITESET_SESSION  to generate dependency information from the source’s write set, transaction_write_set_extraction  must be set or defaulted to specify an algorithm (not set to OFF ). While the current value of  binlog_transaction_dependency_tracking  is  WRITESET  or WRITESET_SESSION , you cannot change the value of  transaction_write_set_extraction . As of MySQL 8.0.14, setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. See Section 5.1.9.1, “System Variable Privileges” .  binlog_format  must be set to  ROW  to change the value of this system variable. The MySQL Server system variables described in this section are used to monitor and control Global Transaction Identifiers (GTIDs). For additional information, see Section 17.1.3, “Replication with Global Transaction Identifiers” . 17.1.6.5 Global Transaction ID System Variables • binlog_gtid_simple_recovery Command-Line Format --binlog-gtid-simple-recovery[={OFF| ON}] System Variable binlog_gtid_simple_recovery Scope Global Dynamic No SET_VAR  Hint Applies No Type Boolean Default Value ON This variable controls how binary log files are iterated during the search for GTIDs when MySQL starts or restarts. When  binlog_gtid_simple_recovery=TRUE , which is the default in MySQL 8.0, the values of  gtid_executed  and  gtid_purged  are computed at startup based on the values of Previous_gtids_log_event  in the most recent and oldest binary log files. For a description of the computation, see The  gtid_purged  System Variable. This setting accesses only two binary log files during server restart. If all binary logs on the server were generated using MySQL 5.7.8 or later, binlog_gtid_simple_recovery=TRUE  can always safely be used. 3570