Compatibility and removed items in 8.4¶

A successful migration requires identifying and addressing all removed parameters, variables, and functions. Using removed items in configuration files or application code will cause errors and prevent server startup or application execution.

Removed server and replication system variables¶

Variable Name	Description	Replacement
`avoid_temporal_upgrade`	Whether ALTER TABLE should upgrade pre-5.6.4 temporal columns	No replacement
`binlog_transaction_dependency_tracking`	Source of dependency information for multithreaded applier	Functionality is now internal; WRITESET is the default and the only available mode
`character-set-client-handshake`	Do not ignore client-side character set value sent during handshake	No replacement
`default_authentication_plugin`	Default authentication plugin	`authentication_policy`
`expire_logs_days`	Purge binary logs after a number of days	`binlog_expire_logs_seconds`
`group_replication_ip_whitelist`	List of hosts permitted to connect to the group	No replacement
`group_replication_primary_member`	Primary member UUID when in single-primary mode	No replacement
`group_replication_recovery_complete_at`	Recovery policies when handling cached transactions	No replacement
`have_openssl`	Whether the server supports SSL connections	No replacement
`have_ssl`	Whether the server supports SSL connections	No replacement
`innodb_api_...` variables	All innodb_api variables related to built-in memcached functionality	No replacement

Removed server options, SQL statements, and status variables¶

Item Name	Type	Replacement
`admin-ssl`	Server Option	`--tls-version` and `--admin-tls-version`
`authentication_fido_rp_id`	Server Option	No replacement
`--language`	Server Option	No replacement
`--old` and `--new`	Server Option	No replacement
`Com_change_master`	Status Variable	`Com_change_replication_source`
`Com_show_master_status`	Status Variable	`Com_show_binary_log_status`
`Com_show_slave_status`	Status Variable	`Com_show_replica_status`
`Com_slave_start`	Status Variable	`Com_replica_start`
`Com_slave_stop`	Status Variable	`Com_replica_stop`
`CHANGE MASTER TO`	SQL Statement	`CHANGE REPLICATION SOURCE TO`
`SHOW SLAVE STATUS`	SQL Statement	`SHOW REPLICA STATUS`
`START SLAVE`	SQL Statement	`START REPLICA`
`STOP SLAVE`	SQL Statement	`STOP REPLICA`
`SHOW MASTER STATUS`	SQL Statement	`SHOW BINARY LOG STATUS`
`RESET MASTER`	SQL Statement	`RESET BINARY LOGS AND GTIDS`
`WAIT_UNTIL_SQL_THREAD_AFTER_GTIDS()`	SQL Function	`WAIT_FOR_EXECUTED_GTID_SET()`

Third-party tool compatibility¶

Percona XtraBackup (PXB)¶

Version-specific backups: Percona XtraBackup 8.4 creates backups of MySQL 8.4, Percona Server for MySQL 8.4, and Percona XtraDB Cluster 8.4 only.
Compatibility: Does not support backing up databases from MySQL 8.0 or 9.x servers.
Action: Upgrade XtraBackup to version 8.4 before or during the database upgrade.

Percona Operator for MySQL¶

Upgrade method: Create a new PXC 8.4 installation using the Percona Operator for PXC 8.4.
Data migration: Recover data from an 8.0 backup, then establish asynchronous replication between clusters.
In-place upgrade: Not recommended; may work but is not guaranteed.

ProxySQL¶

MySQL 8.4 support: Recent versions support MySQL 8.4 and include Group Replication support for 8.4 and 9.x.
Authentication: ProxySQL 2.6+ supports caching_sha2_password (default in 8.4).
Replication terminology: Compatible with SOURCE/REPLICA syntax; can monitor replica lag and manage traffic accordingly.

Pre-upgrade validation¶

Use these tools to identify compatibility issues:

mysqlsh upgrade checker: Identifies many removed parameters and compatibility issues.
Manual review: Cross-reference your configuration files and application code against the removed items tables above.
Third-party tooling: Verify versions of backup utilities, proxies, and monitoring solutions.