PolarDB uses a two-level parameter system: cluster parameters apply to every node in the cluster, while node parameters apply to a single node. After creating a cluster, you can modify both types through the PolarDB console, export the current settings as a reusable parameter template, and compare parameter values across nodes.
How it works
Cluster parameters vs. node parameters
| Type | Scope | When to use |
|---|---|---|
| Cluster parameter | All nodes in the cluster | Apply a setting uniformly, such as adjusting connection limits or query cache behavior |
| Node parameter | A single node only | Fine-tune a specific node, such as adjusting innodb_buffer_pool_size for the primary node |
When you modify a cluster parameter, PolarDB applies it to all nodes immediately (or after a restart, if the parameter requires one). When you modify a node parameter, only that node is affected — other nodes retain their current values.
Parameter inheritance during failover
When a new node joins the cluster, it automatically inherits the cluster's current parameter settings.
During a primary node failover, both the original primary (now read-only) and the original read-only node (now primary) retain their own parameter settings unchanged.
When the primary zone fails and a node in the secondary zone becomes the new primary, the cluster's parameter settings are applied to that node.
Static vs. dynamic parameters
Parameters with Force Restart set to Yes are static — changes take effect only after all nodes in the cluster are restarted. Parameters without a restart requirement take effect immediately after you submit the change. Check the Force Restart column before modifying a parameter to plan for any service impact.
Prerequisites
Before you begin, ensure that you have:
A PolarDB for MySQL cluster
The permissions required to modify cluster or node parameters in the PolarDB console
Usage notes
All parameters in the PolarDB console are prefixed with
loose_for MySQL configuration file compatibility. For example,loose_rds_audit_log_event_buffer_sizeandrds_audit_log_event_buffer_sizebehave identically — modify theloose_-prefixed version in the console.Only a subset of node parameters can be modified in the console:
PolarDB for MySQL 5.6 and 5.7:
innodb_buffer_pool_sizePolarDB for MySQL 8.0:
innodb_buffer_pool_size,loose_oss_outfile_buffer_size,loose_max_oss_outfile_threads,loose_csv_oss_buff_size
To modify node parameters not listed above, go to Quota Center and click Apply in the Actions column for the Set cluster parameters and node parameters quota. In the Reason field, specify the parameters and cluster ID. For additional assistance, contact us.
Modify parameters
Cluster parameters and node parameters share the same workflow — select Cluster or a specific node from the drop-down list to control which scope you are modifying.
Log on to the PolarDB console.
In the upper-left corner, select the region where the cluster is deployed.
Find the cluster and click its ID.
In the left-side navigation pane, choose Settings and Management > Parameters.
In the upper-left corner of the parameters page, select Cluster from the drop-down list to modify cluster parameters, or select a specific node to modify that node's parameters.
Click Modify.
Find the parameter and enter a new value. Values must fall within the range shown in the Range to Be Modified column. Click the
icon next to a parameter name to view its details.Values outside the allowed range trigger an error when you click Submit Changes.
Click Submit Changes.
In the Save Changes panel, select the nodes you want the change to apply to, then click OK.
ImportantIf the parameter's Force Restart value is Yes, the change takes effect only after all nodes in the cluster are restarted. Verify that the restart will not affect your services before proceeding. For PolarDB for MySQL 8.0, set
innodb_fast_startuptoONto speed up the restart.
Export and apply parameter templates
After configuring parameters, you can export the current settings as a reusable template and apply it to other clusters in the same region.
Export the current settings as a template
Follow steps 1–4 in Modify parameters to navigate to the Parameters page.
Click Export as Template.
To include specific changes in the template, modify the parameters first, then export. The exported template includes both parameters you manually modified and parameters that the cluster adjusted automatically during operation.
In the Apply Template dialog box, configure the template.
Parameter Description Template Name Must contain only letters, digits, and underscores ( _); must start with a letter; 8–64 characters in lengthDescription Up to 200 characters Click OK.
Apply a template to a cluster
Follow steps 1–4 in Modify parameters to navigate to the Parameters page.
Click Apply Template.
In the Apply Template dialog box, select the template name and click OK. The dialog shows the number of parameters affected, whether a restart is required, and the last update time of the template.
ImportantIf the template requires a restart, apply it during off-peak hours and make sure your application can automatically reconnect to the cluster after the restart.
You can also apply templates from the Parameter Templates page. For details, see Apply a parameter template.
Compare parameter settings across nodes
Use the parameter comparison feature to identify differences between nodes — for example, after a failover or when troubleshooting inconsistent behavior.
Log on to the PolarDB console.
In the upper-left corner, select the region where the cluster is deployed.
Find the cluster and click its ID.
In the left-side navigation pane, choose Settings and Management > Parameters.
Click Compare.
Select the nodes to compare. The comparison results display immediately.
API reference
| Operation | Description |
|---|---|
| DescribeDBClusterParameters | Queries cluster parameters |
| ModifyDBClusterParameters | Modifies cluster parameters |
| ModifyDBClusterAndNodesParameters | Modifies cluster parameters and applies them to specified nodes |
| ModifyDBNodesParameters | Modifies the parameters of a single node and applies them to the node |
| DescribeParameterTemplates | Queries the default parameters in a parameter template |