Parameter list

Notes when changing parameters

The parameter list and basic concepts provided by KakaoCloud MySQL follow the MySQL official documentation. Changing parameters may affect MySQL service operation, so review the purpose and values of each parameter before making changes.

Parameters to be careful when modifying

Some parameters can affect memory usage, connection count, character set, search features, and other behavior. Before changing them, check the instance specifications, workload, and dependencies between parameters.

InnoDB memory and log parameters

Parameter	Purpose	Notes when modifying
innodb_buffer_pool_size	Sets the InnoDB buffer pool size	If too small, performance may degrade. If too large, system memory may become insufficient Configure based on instance group specifications and workload - Reserved expression example: {kc.InstanceMemory * 6 / 10} - Depending on MySQL buffer pool management, it may be readjusted to a multiple of {innodb_buffer_chunk_size * innodb_buffer_pool_instances}
innodb_buffer_pool_chunk_size	Sets the chunk size used when allocating the InnoDB buffer pool	If too small, memory allocation efficiency may decrease. If too large, initialization time may increase Check its relationship with innodb_buffer_pool_size - Changing this value may automatically increase innodb_buffer_pool_size
innodb_buffer_pool_instances	Sets the number of instances that divide the InnoDB buffer pool	If too low, contention may degrade performance. If too high, memory may be wasted Configure based on instance group specifications - Reserved expression example: { MIN(kc.InstanceVcpu * 2, 64) }
innodb_redo_log_capacity	Sets the total InnoDB redo log capacity	If too small, performance may degrade because log files fill up quickly. If too large, disk usage may increase Check transaction volume and log storage usage

Connection and time setting parameters

Parameter	Purpose	Notes when modifying
max_connections	Sets the maximum number of concurrent connections allowed to the MySQL server	If too low, connections may fail. If too high, resource usage may increase Configure based on instance group specifications and application connection count - Reserved expression example: { MIN(kc.InstanceMemory / 12582880, 16000) }
time_zone	Sets the MySQL server time zone	Incorrect time zone settings may cause timestamp and time-related data errors The time zone of each connecting client can be initialized - Available value examples: system, +00:00, +01:00

Character set and collation parameters

Notes when changing character sets and collations

character_set_* and collation_* parameters must be set to compatible values. In particular, character_set_server and collation_server are related, so changing only one value may cause MySQL to automatically adjust it to a value that matches the same character set. Before changing them, see the MySQL official documentation for character sets, character set and collation compatibility, and server character set and collation.

Parameter	Purpose	Notes when modifying
character_set_client character_set_connection character_set_filesystem character_set_results character_set_server	Specifies the character set used in databases, tables, and columns	Incorrect settings may cause data corruption, performance degradation, or compatibility issues Select a character set appropriate for the environment and check compatibility with collation_* parameters
collation_connection collation_server	Sets string comparison and sorting rules within a specific character set	Incorrect settings may cause data integrity issues, performance degradation, or compatibility issues Set a collation compatible with character_set_* parameters
character_set_server collation_server	Sets the default character set and collation for the MySQL server	Changing only one value may cause MySQL to automatically adjust it to a value that matches the same character set Change both parameters together as a compatible combination - Example: If only character_set_server is changed to big5, the collation_server value shown in the console may differ from the value actually applied in the DB

Feature dependency parameters

Parameter	Purpose	Notes when modifying
innodb_ft_aux_table	Specifies the auxiliary table for InnoDB full-text search	Incorrect settings may cause full-text search issues Condition for normal operation: enter an existing table name - If a non-existent table is entered, normal operation cannot be verified

Expressions, functions, and reserved keywords used in parameters

Some parameters in custom parameter groups support expressions, functions, and reserved keywords. These can only be used with numeric and string type parameters.
The result of any expression must be within the range of a 64-bit signed integer (-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807).
If the result exceeds this range, it will not be accepted.

Category	Description
Expression	Must always be written within {}
	Can use (), +, -, *, /
	Result must always be a number
	For INTEGER data types, decimals are truncated
Function	MAX(a, b, ...): Returns the largest value. Must be uppercase.
	MIN(a, b, ...): Returns the smallest value. Must be uppercase.
	SUM(a, b, ...): Returns the sum. Must be uppercase.
	IF(condition, a, b): Returns a if true, b if false. Must be uppercase.
Reserved Keywords	kc.InstanceMemory: Memory size (bytes) of the current DB instance type
	kc.InstanceVcpu: Number of vCPU cores in the DB instance
	kc.VolumeSizeData: Data volume size
	kc.VolumeSizeLog: Log volume size
	kc.InstanceCount: Total number of nodes
	kc.InstancePrimaryCount: Number of Primary nodes
	kc.InstanceStandbyCount: Number of Standby nodes
	kc.InstanceGroupId: Instance group ID

Usage example

Below is an example using the default value for max_connections.

Example
Returns the smaller of the two values: result of kc.InstanceMemory / 12582880 (rounded down), and 16000.

{ MIN(kc.InstanceMemory / 12582880, 16000) }