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add a better clarification on how sysvar changes "propagate" (#5562) #5641

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May 18, 2021
Merged

add a better clarification on how sysvar changes "propagate" (#5562) #5641

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add a better clarification on gvc
morgo May 5, 2021
83b6a4f
Update system-variables.md
morgo May 17, 2021
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2 changes: 1 addition & 1 deletion system-variables.md
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Expand Up @@ -25,7 +25,7 @@ SET GLOBAL tidb_distsql_scan_concurrency = 10;

> **Note:**
>
> TiDB differs from MySQL in that `GLOBAL` scoped variables **persist** through TiDB server restarts. Changes are also propagated to other TiDB servers every 2 seconds [TiDB #14531](https://github.com/pingcap/tidb/issues/14531).
> TiDB differs from MySQL in that `GLOBAL` scoped variables **persist** through TiDB server restarts. Changes to `GLOBAL` variables might take up to 2 seconds to be effective, including on the TiDB server where the changes are made. See [TiDB #14531](https://github.com/pingcap/tidb/issues/14531) for details.
> Additionally, TiDB presents several MySQL variables from MySQL 5.7 as both readable and settable. This is required for compatibility, since it is common for both applications and connectors to read MySQL variables. For example: JDBC connectors both read and set query cache settings, despite not relying on the behavior.

## Variable Reference
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