Note:
This topic has been translated from a Chinese forum by GPT and might contain errors.
Original topic: 参数配置生效问题
[TiDB Usage Environment] Production Environment
[TiDB Version] v4.0.10
[Encountered Problem]
Problem Description: When expanding drainer with tiup, the parameter was not closed. Later, the drainer.toml was modified and took effect after restarting. After a period of time, drainer restarted, and it seems that the [sync ddl] parameter became the default again?
Dear experts, can it only take effect permanently after modifying the metadata? Additionally, are there any recommended documents related to large table DDL?
DDL for large tables in 4.x… seems like there’s no feature support, just a bunch of pitfalls… 
There are actually several ways to modify configurations, for example:
- File configuration
- In-memory configuration
- Global in-memory configuration
- Automatic loading configuration with tiup
Each corresponds to different scenarios and parameters…
As for the configuration of driner.toml, there are two ways to modify it:
- Through
tiup edit-config
, by overriding parameters to replace the default values
- By adjusting the configuration information in the local deploy directory’s toml to ensure successful loading, which is quite troublesome…
- Or by specifying a configuration file to make the configuration effective…
You can refer to this:
I also have version 4.0x here. It was upgraded from 2.0, and it’s very bad. I’m afraid to modify any parameters. It feels safe only if it’s upgraded to at least 6.5 or above.
Old versions can be worrisome; it’s best to upgrade.