# Dynamically Modifying TiDB Configuration File Parameters

__*Online modify of TiDB cluster configuration*__
__*Online modify of TiDB cluster parameters*__
__*zz-BGL*__
__*zz-Jeff*__

+ TiKV configuration
  + Modify the configuration for TiKV cluster:
    + **`SET CONFIG TIKV split.qps-threshold=1000;`**
  + Modify the configuration of a single TiKV instance, for example:
    + **`SET CONFIG '127.0.0.1:20180' split.qps-threshold=1000;`**
+ Placement Driver configuration
  + **`SET CONFIG PD log.level='info';`**
+ Note that
  + Only some of the configuration file parameters can be modified dynamically
  + Operations such as `upgrade` and `reload` will overwrite your changes, if you modify TiDB configuration file parameters dynamically. To avoid this, you also need to modify the corresponding configuration items by executing `tiup cluster edit-config <cluster-name>`


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You can update the configuration of components (including `TiDB`, `TiKV`, and `PD`) online using `SQL` statements, without restarting the cluster components. Currently, the method of changing `TiDB` instance configuration is different from that of changing configuration of other components (such `TiKV` and `PD`).

When using the set config statement, you can modify the configuration of a single instance or of all instances according to the instance address or the component type.

The batch modification does not guarantee atomicity. The modification might succeed on some instances, while failing on others. If you modify the configuration of the entire `TiKV` cluster using `set config tikv key=val`, your modification might fail on some instances. You can use `show warnings` to check the result.