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This topic has been translated from a Chinese forum by GPT and might contain errors.Original topic: 求准确答案
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username: Running
Is the answer C correct?
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username: Running
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username: Is this a homework exercise or an exam question?
If it’s a homework exercise, it was explained in the course.
If it’s an exam question, then this post might disappear.
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username: The official documentation states that no restart is required.
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username: 
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username: This is how I understand it: configuration refers to the settings in the configuration file 
, and those set are called environment variables.
From this perspective, modifying the configuration requires a restart. TiKV, TiDB, and PD don’t have a reload feature like Nginx, right?
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username: Online modification of cluster configuration parameters is actually an experimental feature. It can take effect, but you still need to use the tiup edit-config command to modify the corresponding configuration items. Otherwise, operations such as upgrade and reload will overwrite the results of the online configuration modifications. Therefore, you cannot simply modify the configuration online from the client; you need to use it in conjunction with the tiup edit-config command.
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username: Answer: A
C refers to system variables, not cluster parameters.
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username: Yes, isn’t setting the config done by connecting with the MySQL client and then executing it?
After modifying the TiKV configuration items online, the TiKV configuration file will also be automatically modified. However, you still need to use the tiup edit-config command to modify the corresponding configuration items, otherwise operations such as upgrade and reload will overwrite the results of the online configuration modifications.
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username: I went to check the teacher’s explanation, and the answer is indeed A. Modifying the cluster configuration does require a reload to take effect. In option C, modifying cluster parameters can only be done through the tiup cluster edit-config command; it cannot be done using a MySQL client.
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username: 
So you are avoiding my question, is this a screenshot of the PTCA exam question?
There is a difference between cluster configuration and system variables.
After modifying the TiKV configuration items online, the TiKV configuration file will also be automatically modified. However, you still need to use the
tiup edit-configcommand to modify the corresponding configuration items, otherwise operations such asupgradeandreloadwill overwrite the results of the online configuration modifications. For details on modifying configurations, please refer to: Modify Configuration Parameters Using TiUP. After executingtiup edit-config, there is no need to execute thetiup reloadoperation.
For PD configuration items that can be modified online, once successfully modified, they will be persisted to etcd and will not be persisted to the configuration file. Subsequent operations will be based on the configuration in etcd.