This topic describes the limits of ApsaraDB RDS for MySQL. Before you use ApsaraDB RDS for MySQL, we recommend that you understand these limits. This allows you to ensure the stability and security of your RDS instance.

For more information about the limits of other database engines, see the following topics:

The following table provides details about these limits.

Limit Description
Instance parameters You can reconfigure most of the instance parameters by using the ApsaraDB RDS console or the ApsaraDB RDS API. However, for security and stability purposes, some parameters cannot be reconfigured. For more information, see Use the console to set parameters.
Root permissions The permissions of the root user and system administrator are not provided.
Backup
  • Logical backups can be performed by using the command-line interface (CLI) or the graphical user interface (GUI).
  • Physical backups can be performed only by using the ApsaraDB RDS console or the ApsaraDB RDS API.
Restoration
  • Logical restoration can be performed by using the CLI or the GUI.
  • Physical restoration can be performed only by using the ApsaraDB RDS console or the ApsaraDB RDS API.
Storage engine Only the InnoDB and X-Engine storage engines are supported. For more information about X-Engine, see X-Engine overview.
  • The TokuDB storage engine is not supported. Percona no longer provides support for TokuDB. A number of known issues in TokuDB cannot be fixed. These issues may cause business loss in extreme circumstances. Therefore, ApsaraDB RDS for MySQL has stopped supporting TokuDB since August 1, 2019. For more information about how to switch an RDS instance from TokuDB to another storage engine, see [Notice] The storage engine was switched from TokuDB to InnoDB.
  • The MyISAM storage engine is not supported due to inherent defects that may cause data loss. If you create a MyISAM table, ApsaraDB RDS automatically converts the MyISAM table into an InnoDB table. For more information, see Why does RDS MySQL not support the MyISAM engine?
  • The Memory storage engine is not supported. If you create a Memory table, ApsaraDB RDS automatically converts the Memory table into an InnoDB table.
Replication ApsaraDB RDS for MySQL provides a primary/secondary replication architecture. The secondary RDS instance in this architecture is hidden and cannot be connected to your application. This architecture is not supported in the Basic Edition.
Instance restart You can restart an RDS instance only by using the ApsaraDB RDS console or the ApsaraDB RDS API.
Network settings If an RDS instance runs MySQL 5.5 or MySQL 5.6 in the classic network and the database proxy of the instance is enabled, you cannot enable net.ipv4.tcp_timestamps in SNAT mode.
Storage

If the storage usage of an RDS instance is abnormally high, ApsaraDB RDS locks the instance. This prevents data loss that may be caused by accidental operations. You can unlock the instance by upgrading the specifications of the instance.

Help information If you are using MySQL 8.0, you can query detailed help information from the mysql.help_topic table. If you are not using MySQL 8.0, the mysql.help_topic table is empty.
Number of instances The number of pay-as-you-go RDS instances that you can create is limited to 30. You can go to the Quota Center console to increase the limit.