## Overview

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> [!NOTE]
> - This lab only supports Chrome browser.

In TiDB, there are TiDB system variables and TiDB configuration file parameters to control the TiDB cluster behaviors. In these exercises, you gain experience on modifying TiDB system variables and TiDB configuration file parameters.

For TiDB system variables, there are four categories based on the effective scope.

  | Category              | Change By     | Effective Scope                                         |
  | :-------------------- | :------------ | :------------------------------------------------------ |
  | Session Only          | `SET SESSION` | Current Session                                         |
  | Global Persistent     | `SET GLOBAL`  | All TiDB Server Instances and All Sessions              |
  | Global Non-Persistent | `SET GLOBAL`  | Current TiDB Server Instance and its Connected Sessions |
  | Session and Global    | `SET SESSION` | Current Session                                         |
  | Session and Global    | `SET GLOBAL`  | All TiDB Server Instances and New Sessions              |

> [!TIP]
> Click **Start** to launch the lab environment.
> Once the environment is ready, select **Next** on the bottom toolbar to advance to **Module 1**.
> And, follow the step-by-step lab guide to connect to the hands-on environment and begin your tasks.