- `binlog_gtid_simple_recovery`

  Property | Value
  --- | ---
  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.

  If any binary logs from MySQL 5.7.7 or older are present on the server (for example, following an upgrade of an older server to MySQL 8.0), with `binlog_gtid_simple_recovery=TRUE`, `gtid_executed` and `gtid_purged` might be initialized incorrectly in the following two situations:

  - The newest binary log was generated by MySQL 5.7.5 or earlier, and `gtid_mode` was `ON` for some binary logs but `OFF` for the newest binary log.

  - A `SET @@GLOBAL.gtid_purged` statement was issued on MySQL 5.7.7 or earlier, and the binary log that was active at the time of the `SET @@GLOBAL.gtid_purged` statement has not yet been purged.

  If an incorrect GTID set is computed in either situation, it will remain incorrect even if the server is later restarted with `binlog_gtid_simple_recovery=FALSE`. If either of these situations apply or might apply on the server, set `binlog_gtid_simple_recovery=FALSE` before starting or restarting the server.

  When `binlog_gtid_simple_recovery=FALSE` is set, the method of computing `gtid_executed` and `gtid_purged` as described in The `gtid_purged` System Variable is changed to iterate the binary log files as follows:

  - Instead of using the value of `Previous_gtids_log_event` and GTID log events from the newest binary log file, the computation for `gtid_executed` iterates from the newest binary log file, and uses the value of `Previous_gtids_log_event` and any GTID log events from the first binary log file where it finds a `Previous_gtids_log_event` value. If the server's most recent binary log files do not have GTID log events, for example if `gtid_mode=ON` was used but the server was later changed to `gtid_mode=OFF`, this process can take a long time.

  - Instead of using the value of `Previous_gtids_log_event` from the oldest binary log file, the computation for `gtid_purged` iterates from the oldest binary log file, and uses the value of `Previous_gtids_log_event` from the first binary log file where it finds either a nonempty `Previous_gtids_log_event` value, or at least one GTID log event (indicating that the use of GTIDs starts at that point). If the server's older binary log files do not have GTID log events, for example if `gtid_mode=ON` was only set recently on the server, this process can take a long time.

- `enforce_gtid_consistency`

  Property | Value
  --- | ---
  Command-Line Format | `--enforce-gtid-consistency[=value]`
  System Variable | `enforce_gtid_consistency`
  Scope | Global
  Dynamic | Yes
  `SET_VAR` Hint Applies | No
  Type | Enumeration
  Default Value | `OFF`
  Valid Values | `OFF` `ON` `WARN`

  Depending on the value of this variable, the server enforces GTID consistency by allowing execution of only statements that can be safely logged using a GTID. You must set this variable to `ON` before enabling GTID based replication.

  The values that `enforce_gtid_consistency` can be configured to are:

  - `OFF`: all transactions are allowed to violate GTID consistency.

  - `ON`: no transaction is allowed to violate GTID consistency.

  - `WARN`: all transactions are allowed to violate GTID consistency, but a warning is generated in this case.

  Only statements that can be logged using GTID safe statements can be logged when `enforce_gtid_consistency` is set to `ON`, so the operations listed here cannot be used with this option:

  - `CREATE TABLE ... SELECT` statements

  - `CREATE TEMPORARY TABLE` or `DROP TEMPORARY TABLE` statements inside transactions

  - Transactions or statements that update both transactional and nontransactional tables. There is an exception that nontransactional DML is allowed in the same transaction or in the same statement as transactional DML, if all nontransactional tables are temporary.

  `--enforce-gtid-consistency` only takes effect if binary logging takes place for a statement. If binary logging is disabled on the server, or if statements are not written to the binary log because they are removed by a filter, GTID consistency is not checked or enforced for the statements that are not logged.

  For more information, see Section 17.1.3.6, “Restrictions on Replication with GTIDs”.

  Prior to MySQL 5.7 and in early releases in that release series, the boolean `enforce_gtid_consistency` defaulted to `OFF`. To maintain compatibility with these earlier releases, the enumeration defaults to `OFF`, and setting `--enforce-gtid-consistency` without a value is interpreted as setting the value to `ON`. The variable also has multiple textual aliases for the values: `0=OFF=FALSE`, `1=ON=TRUE`,`2=WARN`. This differs from other enumeration types but maintains compatibility with the boolean type used in previous releases. These changes impact on what is returned by the variable. Using `SELECT @@ENFORCE_GTID_CONSISTENCY`, `SHOW VARIABLES LIKE 'ENFORCE_GTID_CONSISTENCY'`, and `SELECT * FROM INFORMATION_SCHEMA.VARIABLES WHERE 'VARIABLE_NAME' = 'ENFORCE_GTID_CONSISTENCY'`, all return the textual form, not the numeric form. This is an incompatible change, since `@@ENFORCE_GTID_CONSISTENCY` returns the numeric form for booleans but returns the textual form for `SHOW` and the Information Schema.

- `gtid_executed`

  Property | Value
  --- | ---
  System Variable | `gtid_executed`
  System Variable | `gtid_executed`
  Scope | Global
  Scope | Global, Session
  Dynamic | No
  Dynamic | No
  `SET_VAR` Hint Applies | No
  `SET_VAR` Hint Applies | No
  Type | String

  When used with global scope, this variable contains a representation of the set of all transactions executed on the server and GTIDs that have been set by a `SET` `gtid_purged` statement. This is the same as the value of the `Executed_Gtid_Set` column in the output of `SHOW MASTER STATUS` and `SHOW SLAVE STATUS`. The value of this variable is a GTID set, see GTID Sets for more information.

  When the server starts, `@@GLOBAL.gtid_executed` is initialized. See `binlog_gtid_simple_recovery` for more information on how binary logs are iterated to populate `gtid_executed`. GTIDs are then added to the set as transactions are executed, or if any `SET` `gtid_purged` statement is executed.

  The set of transactions that can be found in the binary logs at any given time is equal to `GTID_SUBTRACT(@@GLOBAL.gtid_executed, @@GLOBAL.gtid_purged)`; that is, to all transactions in the binary log that have not yet been purged.

  Issuing `RESET MASTER` causes the global value (but not the session value) of this variable to be reset to an empty string. GTIDs are not otherwise removed from this set other than when the set is cleared due to `RESET MASTER`.

  In some older releases, this variable could also be used with session scope, where it contained a representation of the set of transactions that are written to the cache in the current session. The session scope is now deprecated.

- `gtid_executed_compression_period`

  Property | Value
  --- | ---
  Command-Line Format | `--gtid-executed-compression-period=#`
  System Variable | `gtid_executed_compression_period`
  Scope | Global
  Dynamic | Yes
  `SET_VAR` Hint Applies | No
  Type | Integer
  Default Value | `1000`
  Minimum Value | `0`
  Maximum Value | `4294967295`

  Compress the `mysql.gtid_executed` table each time this many transactions have been processed. A setting of 0 means that this table is not compressed. Since no compression of the table occurs when using the binary log, setting the value of the variable has no effect unless binary logging is disabled.

  See mysql.gtid_executed Table Compression, for more information.

- `gtid_mode`

  Property | Value
  --- | ---
  Command-Line Format | `--gtid-mode=MODE`
  System Variable | `gtid_mode`
  Scope | Global
  Dynamic | Yes
  `SET_VAR` Hint Applies | No
  Type | Enumeration
  Default Value | `OFF`
  Valid Values | `OFF` `OFF_PERMISSIVE` `ON_PERMISSIVE` `ON`

  Controls whether GTID based logging is enabled and what type of transactions the logs can contain. You must have privileges sufficient to set global system variables. See Section 5.1.9.1, “System Variable Privileges”. `enforce_gtid_consistency` must be true before you can set `gtid_mode=ON`. Before modifying this variable, see Section 17.1.5, “Changing Replication Modes on Online Servers”.

  Logged transactions can be either anonymous or use GTIDs. Anonymous transactions rely on binary log file and position to identify specific transactions. GTID transactions have a unique identifier that is used to refer to transactions. The different modes are:

  - `OFF`: Both new and replicated transactions must be anonymous.

  - `OFF_PERMISSIVE`: New transactions are anonymous. Replicated transactions can be either anonymous or GTID transactions.

  - `ON_PERMISSIVE`: New transactions are GTID transactions. Replicated transactions can be either anonymous or GTID transactions.

  - `ON`: Both new and replicated transactions must be GTID transactions.

  Changes from one value to another can only be one step at a time. For example, if `gtid_mode` is currently set to `OFF_PERMISSIVE`, it is possible to change to `OFF` or `ON_PERMISSIVE` but not to `ON`.

  The values of `gtid_purged` and `gtid_executed` are persistent regardless of the value of `gtid_mode`. Therefore even after changing the value of `gtid_mode`, these variables contain the correct values.

- `gtid_next`

  Property | Value
  --- | ---
  System Variable | `gtid_next`
  Scope | Session
  Dynamic | Yes
  `SET_VAR` Hint Applies | No
  Type | Enumeration
  Default Value | `AUTOMATIC`
  Valid Values | `AUTOMATIC` `ANONYMOUS` `UUID:NUMBER`

  This variable is used to specify whether and how the next GTID is obtained.

  Setting the session value of this system variable is a restricted operation. The session user must have either the `REPLICATION_APPLIER` privilege (see Section 17.3.3, “Replication Privilege Checks”), or privileges sufficient to set restricted session variables (see Section 5.1.9.1, “System Variable Privileges”).

  `gtid_next` can take any of the following values:

  - `AUTOMATIC`: Use the next automatically-generated global transaction ID.

  - `ANONYMOUS`: Transactions do not have global identifiers, and are identified by file and position only.

  - A global transaction ID in `UUID`:`NUMBER` format.

  Exactly which of the above options are valid depends on the setting of `gtid_mode`, see Section 17.1.5.1, “Replication Mode Concepts” for more information. Setting this variable has no effect if `gtid_mode` is `OFF`.

  After this variable has been set to `UUID`:`NUMBER`, and a transaction has been committed or rolled back, an explicit `SET GTID_NEXT` statement must again be issued before any other statement.

  `DROP TABLE` or `DROP TEMPORARY TABLE` fails with an explicit error when used on a combination of nontemporary tables with temporary tables, or of temporary tables using transactional storage engines with temporary tables using nontransactional storage engines.

- `gtid_owned`

  Property | Value
  --- | ---
  System Variable | `gtid_owned`
  Scope | Global, Session
  Dynamic | No
  `SET_VAR` Hint Applies | No
  Type | String

  This read-only variable is primarily for internal use. Its contents depend on its scope.

  - When used with global scope, `gtid_owned` holds a list of all the GTIDs that are currently in use on the server, with the IDs of the threads that own them. This variable is mainly useful for a multi-threaded replication slave to check whether a transaction is already being applied on another thread. An applier thread takes ownership of a transaction's GTID all the time it is processing the transaction, so `@@global.gtid_owned` shows the GTID and owner for the duration of processing. When a transaction has been committed (or rolled back), the applier thread releases ownership of the GTID.

  - When used with session scope, `gtid_owned` holds a single GTID that is currently in use by and owned by this session. This variable is mainly useful for testing and debugging the use of GTIDs when the client has explicitly assigned a GTID for the transaction by setting `gtid_next`. In this case, `@@session.gtid_owned` displays the GTID all the time the client is processing the transaction, until the transaction has been committed (or rolled back). When the client has finished processing the transaction, the variable is cleared. If `gtid_next=AUTOMATIC` is used for the session, `gtid_owned` is only populated briefly during the execution of the commit statement for the transaction, so it cannot be observed from the session concerned, although it will be listed if `@@global.gtid_owned` is read at the right point. If you have a requirement to track the GTIDs that are handled by a client in a session, you can enable the session state tracker controlled by the `session_track_gtids` system variable.

- `gtid_purged`

  Property | Value
  --- | ---
  System Variable | `gtid_purged`
  Scope | Global
  Dynamic | Yes
  `SET_VAR` Hint Applies | No
  Type | String

  The global value of the `gtid_purged` system variable (`@@GLOBAL.gtid_purged`) is a GTID set consisting of the GTIDs of all the transactions that have been committed on the server, but do not exist in any binary log file on the server. `gtid_purged` is a subset of `gtid_executed`. The following categories of GTIDs are in `gtid_purged`:

  - GTIDs of replicated transactions that were committed with binary logging disabled on the slave.

  - GTIDs of transactions that were written to a binary log file that has now been purged.

  - GTIDs that were added explicitly to the set by the statement `SET @@GLOBAL.gtid_purged`.

  When the server starts, the global value of `gtid_purged` is initialized to a set of GTIDs. For information on how this GTID set is computed, see The `gtid_purged` System Variable. If binary logs from MySQL 5.7.7 or older are present on the server, you might need to set `binlog_gtid_simple_recovery=FALSE` in the server's configuration file to produce the correct computation. See the description for `binlog_gtid_simple_recovery` for details of the situations in which this setting is needed.

  Issuing `RESET MASTER` causes the value of `gtid_purged` to be reset to an empty string.

  You can set the value of `gtid_purged` in order to record on the server that the transactions in a certain GTID set have been applied, although they do not exist in any binary log on the server. An example use case for this action is when you are restoring a backup of one or more databases on a server, but you do not have the relevant binary logs containing the transactions on the server.

  From MySQL 8.0, there are two ways to set the value of `gtid_purged`. You can either replace the value of `gtid_purged` with your specified GTID set, or you can append your specified GTID set to the GTID set that is already held by `gtid_purged`. If the server has no existing GTIDs, for example an empty server that you are provisioning with a backup of an existing database, both methods have the same result. If you are restoring a backup that overlaps the transactions that are already on the server, for example replacing a corrupted table with a partial dump from the master made using mysqldump (which includes the GTIDs of all the transactions on the server, even though the dump is partial), use the first method of replacing the value of `gtid_purged`. If you are restoring a backup that is disjoint from the transactions that are already on the server, for example provisioning a multi-source replication slave using dumps from two different servers, use the second method of adding to the value of `gtid_purged`.

  - To replace the value of `gtid_purged` with your specified GTID set, use the following statement:

        Press CTRL+C to copy SET @@GLOBAL.gtid_purged = 'gtid_set'

    `gtid_set` must be a superset of the current value of `gtid_purged`, and must not intersect with `gtid_subtract(gtid_executed,gtid_purged)`. In other words, the new GTID set must include any GTIDs that were already in `gtid_purged`, and must not include any GTIDs in `gtid_executed` that have not yet been purged. `gtid_set` also cannot include any GTIDs that are in `@@global.gtid_owned`, that is, the GTIDs for transactions that are currently being processed on the server.

    The result is that the global value of `gtid_purged` is set equal to `gtid_set`, and the value of `gtid_executed` becomes the union of `gtid_set` and the previous value of `gtid_executed`.

  - To append your specified GTID set to `gtid_purged`, use the following statement with a plus sign (+) before the GTID set:

        Press CTRL+C to copy SET @@GLOBAL.gtid_purged = '+gtid_set'

    `gtid_set` must not intersect with the current value of `gtid_executed`. In other words, the new GTID set must not include any GTIDs in `gtid_executed`, including transactions that are already also in `gtid_purged`. `gtid_set` also cannot include any GTIDs that are in `@@global.gtid_owned`, that is, the GTIDs for transactions that are currently being processed on the server.

    The result is that `gtid_set` is added to both `gtid_executed` and `gtid_purged`.