Create and manage parameter groups

A parameter group lets you view MySQL parameters by engine version and manage settings applied to connected instance groups.

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.

Event notifications

• You can receive notifications for events such as creation and modification of parameter groups through Alert Center > Event Notification.
  
• For available event types, see Cloud Trail > Concepts, and for setting alerts, refer to Alert Center > Creating and Managing Alert Policies.

View parameter group list

You can check the list of parameter groups, including default and custom groups, provided by KakaoCloud MySQL.

1. Go to the KakaoCloud Console > Data Store > MySQL.

2. Click the Parameter Groups menu and choose either the Custom Groups or Default Groups tab.

3. The corresponding parameter group list will be displayed.

   Item	Description
   Name	Name of the parameter group
   Engine Version	MySQL engine version compatible with the parameter group
   Connected Instance Groups	Number of instance groups connected to this parameter group - A warning icon is shown if there's an issue with parameter application status
   Description	Description of the parameter group
   [⋮] button	Available only for custom groups: - Edit: Modify parameters - Copy: Create a new group with the same parameters - Reset to Default: Restore parameters to their initial values - Rollback: Revert to previous values if available - Delete: Delete the group

View parameter group details

You can view detailed information about a MySQL parameter group.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Groups menu and choose either the Custom Groups or Default Groups tab.
3. Select the desired parameter group to view its details.

Tab: Parameters

Depending on the parameter type, such as Static, modifying a parameter may require an instance restart.

Item	Description
Name	Parameter name
Value	Parameter value
Type	Parameter type: Static, Dynamic - Static requires a restart when applied - Some Dynamic parameters require session refresh as they apply globally
Data Type	Data type of the parameter
Editable	Not Editable, Editable, Editable (Modified) - Only Editable parameters can be changed. If modified, they are marked as Editable (Modified)

Tab: Connected instance groups

Item	Description
Name	Name of the instance group
Status	Status of the instance group
Parameter Application Status	Current status of parameter application - See Parameter Application Status for details
Engine Version	MySQL engine version of the instance group
Instance Type	Type of instance used in the group
Availability	Instance availability: Single, High Availability
[Retry] Button	Retry applying the parameter if the status is Error-Sync or Suspended

Tab: Recent Events

You can check major events that occurred for the parameter group in the past 7 days.

Item	Description
Time	Time the event occurred
Name	Event name
Details	Event details including results and affected instance group

• Recent event types by parameter group:

Group Type	Event Name	Description
Custom Group	Create Parameter Group	Triggered when a new custom group is created
	Update Parameter Group	Triggered when the description of a custom group is updated
	Update Parameter	Triggered when parameter values are updated
	Reset Parameters	Triggered when parameters are reset to default
	Rollback Parameters	Triggered when rollback is requested
	Apply Instance Group	Triggered when parameters are successfully applied
Default Group	Apply Instance Group	Same as above

Create parameter group

1. Go to the KakaoCloud Console > Data Store > MySQL.

2. Click Parameter Groups and select the Custom Groups tab according to the type of parameter group you want to view.

3. In the Custom Groups tab, click the icon > Create Parameter Group.

4. Enter the required information on the Create parameter group page. Parameter values can be modified after the group is created.

   Item	Category	Description
   Basic Settings	Parameter Group Name	Name of the parameter group - Duplicate names cannot be used within the same project
   	Description (Optional)	Additional description up to 100 characters
   Parameter Group Settings	Engine Version	MySQL engine version for the parameter group
   	Default Parameter Group	Select the default parameter group provided for the engine version
   Parameters		Initial parameter values for the group

Modify parameter group

Custom parameter groups allow you to modify descriptions and parameter values after the group is created. Only parameters marked as Editable can be modified. Modified parameters change to Editable (Modified).

Modification notes

• Some Dynamic parameters apply globally and require a session refresh.
• For Static parameters, modifying them triggers a restart of the connected instance groups.
• If the parameter application status is Pending or Applying, parameters cannot be modified.
• Checkboxes remain selected even when navigating through pages within the modifiable parameter list.

Modification cautions

• Some parameters may affect MySQL service operation when modified. Refer to Parameters to be careful when modifying.
• If issues occur after modification, it is recommended to create a parameter group copy for backup, and use retry/rollback/reset options when needed.

1. Go to the KakaoCloud Console > Data Store > MySQL.

2. Click Parameter Groups and navigate to the Custom Groups tab.

3. Select the parameter group you want to modify and click the [⋮] button > Edit.

4. Modify the required values on the Edit Parameter Group page.

   Item	Category	Description
   Basic Information	Parameter Group Name	Name of the parameter group
   	Description (Optional)	Additional description up to 100 characters
   Editable Parameters		List of parameters that can be modified - Modified parameters change to Editable (Modified)

5. Enter values manually or use the Load Existing Parameters feature to import values from an existing custom parameter group, or use Reset to Default to restore initial default values. Click Confirm when finished.

6. If multiple instance groups are connected to the parameter group, select how the parameter updates should be applied.
   Apply All: Apply the modified parameters to all instance groups at once.
   Apply Sequentially: Apply the parameters to each instance group sequentially.

Load existing parameters

You can load parameter values from an existing custom parameter group, regardless of version. Since loaded values replace the existing ones, we recommend saving any necessary information before loading.

1. Go to the Edit parameter group page.
2. In the popup, select the engine version and the target custom parameter group.
3. Review the parameters to be loaded and click Apply.

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) }

Copy Parameter Group

Custom parameter groups provide a copy feature that can be used for backup purposes. You can duplicate a selected parameter group to create a new one.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Group menu and select the Custom Group tab.
3. Find the parameter group you want to copy, click the [⋮] button, and select Copy.
4. In the Copy Parameter Group popup, review the details and click Confirm.
5. Check the copied parameter group in the Custom Group tab.

Reset Parameter Group to Default Values

Custom parameter groups support a reset-to-default feature, which allows you to revert modified parameters back to their default values. The default value is the engine version’s base configuration at the time the group was created. Resetting will attempt to apply parameter changes to all connected instance groups.

Reset notes

• If the parameter application status of a connected instance group is Pending or Applying, you cannot reset parameters to default.
• Resetting a Static parameter will restart the connected instance group.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Group menu and select the Custom Group tab.
3. Locate the group to reset, click the [⋮] button, and select Reset to Default Values.
4. In the reset popup, review the information and click Confirm.
   If the parameter group is connected to multiple instance groups, choose the application method:
   Apply All: Apply changes to all instance groups at once.
   Apply Sequentially: Apply changes one group at a time.
5. For connected instance groups, verify the parameter application status after reset.

Roll back parameter group

Custom parameter groups allow you to roll back parameter values to their previous state after a modification. You can only roll back if there is a modification history immediately before the rollback.

Rollback notes

• You cannot roll back if the parameter application status is Pending or Applying.
• Rolling back a Static parameter will restart the connected instance group.
• Once rollback is performed, previous values are restored and cannot be rolled back again. If new modifications are made, rollback becomes available again.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Group menu and select the Custom Group tab.
3. Find the group to roll back, click the [⋮] button, and select Roll Back.
4. In the rollback popup, review the information and click Confirm.
5. For connected instance groups, verify whether the rollback was applied by checking the parameter application status.

Delete parameter group

If a custom parameter group is no longer needed, it can be deleted.

Deletion notes

• Default parameter groups cannot be deleted.
• If the parameter group is connected to any instance group, it cannot be deleted.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Group menu and select the Custom Group tab.
3. Locate the group to delete, click the [⋮] button, and select Delete.
4. In the delete popup, provide the required information and click Confirm.
5. Verify the deletion in the Custom Group tab.

Retry applying parameter group

You can retry applying a parameter group only when the parameter status of a connected instance is Error-Sync or Suspended (not In-Sync).
For more details on parameter application statuses, refer to Parameter Application Status.

1. Go to the KakaoCloud Console > Data Store > MySQL.
2. Click the Parameter Group menu and select the Custom Group tab.
3. Select the parameter group and go to its Details page.
4. Navigate to the Connected Instance Group tab.
5. Click the Retry button next to the instance you want to retry applying the parameters to.

Check parameter group engine version

If the engine version of an instance group does not match the parameter group, a Check Engine Version badge is displayed. Custom parameter groups with this badge cannot be modified for service stability.

You can check instance groups with mismatched engine versions in the Parameter Group menu > Instance tab. If you use Change parameter group on the instance group and change it to a parameter group that matches the engine version, the badge disappears.

To keep using previously configured parameter values, create a new parameter group that matches the engine version, then use Load Existing Parameters in Modify parameter group.

• Where to check: Parameter Group menu > Instance tab
• Cause: The engine version of the connected instance group and parameter group do not match due to version upgrade or similar work
• Action: Change to a parameter group that matches the engine version