# Case Study: Hotspot

+ Background
  + A **`TPC-C`** benchmark testing
    + **Node configuration:** `128 vCPU`, `512 GB memory`, `4 x 2 TB PCIe SSD`
    + **Version:** `TiDB v6.2`
    + **Hybrid deployment:** `3 (node) x 4 (instance) tidb-server + 6 (node) x 4 (instance) tikv-server + 3 (node) pd-server`
    + **Load:** `10000 warehouse`, `500 concurrency`
  + `200,000 tpmC -> 300,000 tpmC`
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Equivalent statements to change a variable at global scope:
```
SET @@GLOBAL.tidb_distsql_scan_concurrency = 10;
SET GLOBAL TIDB_distsql_scan_concurrency = 10;
```

Equivalent statements to change a variable at session scope:
```
SET tidb_distsql_scan_concurrency = 10;
SET SESSION tidb_distsql_scan_concurrency = 10;
```

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