# Understanding TiDB Configurations

__*TiDB system configuration*__
__*TiDB system variables*__
__*TiDB cluster configuration*__
__*TiDB cluster variables*__

![left](./student-guide/diagram/TiDBConfiguration_en_001_20220617.png)
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We can understand the configuration of the TiDB database as two parts according to the modify method:

The first part is the TiDB system variable. This system variable can be modify by the MySQL client. The system variable specifically refers to the configuration of the TiDB-Server component, excluding the PD and TiKV configurations, which are persisted in the database store.

The second part can be called cluster configuration. The cluster configuration includes the configuration of TIDB-Server, TiKV-Server, and PD. And they are all stored in their own configuration files, and we have to modify them through tiup, and then start each node one by one.