Change Configuration

The count of various types of nodes in a TiDB instance can be adjusted according to changes in business volume, thereby improving the overall processing capacity and data capacity of the instance or reducing the usage cost of the instance.

During configuration change, TiDB instances can be used normally.

Note:

• The configuration can be changed only when the instance is in a “running” status.
• It only supports modifying the count of various types of nodes, and does not support modifying attributes such as CPU core count, memory, or storage space.
• If TiFlash node is not created during creation, it can be added by changing the configuration.

Precondition

When scaling down a TiFlash node, you need to execute the following command for all tables whose replicas are greater than the count of remaining TiFlash nodes in the cluster:

1. Set the count of replicas for the table in TiFlash to 0.

shell
alter table <db-name>.<table-name> set tiflash replica 0;

2. View the count of replicas for the table.

shell
SELECT * FROM information_schema.tiflash_replica WHERE TABLE_SCHEMA = '<db_name>' and TABLE_NAME = '<table_name>';

Operation Steps

1. Login to TiDB Service management console.

2. There are two ingresses for scale-out:

   • Instance list: On the right, click Change configuration.
   • Instance details page: Select the target instance to be scaled out, enter the instance details page, and click Change configuration in the upper right corner of the page.
   • Instance details page: Click Change configuration in the configuration option bar of instance details page.

3. Adjust the count of nodes in the pop-up box for configuration change. When the instance has no TiFlash node to be added, you can select the specification and storage of TiFlash node. When the created instance has TiFlash created, you can only adjust the count of TiFlash nodes.