# Modify of TiDB System Parameters

__*TiDB system configuration scope*__
__*TiDB system variable scope*__
__*TiDB system configuration modify*__
__*Modifying TiDB system variables*__

+ Global scope parameter modify
  + `SET @@global.tidb_distsql_scan_concurrency = 10;`
  + `SET  GLOBAL tidb_distsql_scan_concurrency = 10;`

+ Modifying session scope parameters
  + `SET tidb_distsql_scan_concurrency = 10;`
  + `SET SESSION tidb_distsql_scan_concurrency = 10;`

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The following two statements are equivalent to changing a Global variable
SET @ @global .tidb*distsql*scan_concurrency = 10;
SET GLOBAL TIDB*distsql*scan_concurrency = 10;

Note that the above modify will persist in TiDB's kv store, and will only take effect on new TiDB connection sessions. The current active connection session will not be affected. The changes will be persistent and will remain in effect after a restart.

The following two statements are equivalent to changing a Session variable
SET TIDB*distsql*scan_concurrency = 10;
SET SESSION TIDB*distsql*scan_concurrency = 10;

Note that variables can only be modified temporarily and are not persisted. If you want to persist, you need to manually modify the configuration file of the target TIDB-Server and use tiup edit-config to edit the parameters, but you do not need to perform a tiup reload (this operation will restart indiscriminately).

Please refer to: https://docs.pingcap.com/zh/tidb/stable/system-variables