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cloud: update tidb_dml_type limitation #22415

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ti-chi-bot merged 2 commits into from
Feb 6, 2026
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cloud: update tidb_dml_type limitation #22415

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6104c35
update tidb_dml_type limitation
zuowei593 Feb 6, 2026
1ef3451
add a note in system-variables.md indicating that this variable is re…
qiancai Feb 6, 2026
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4 changes: 4 additions & 0 deletions system-variables.md
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Expand Up @@ -1922,6 +1922,10 @@ Assume that you have a cluster with 4 TiDB nodes and multiple TiKV nodes. In thi
>
> The bulk DML execution mode (`tidb_dml_type = "bulk"`) is an experimental feature. It is not recommended that you use it in the production environment. This feature might be changed or removed without prior notice. If you find a bug, you can report an [issue](https://github.com/pingcap/tidb/issues). In the current version, when TiDB performs large transactions using the bulk DML mode, it might affect the memory usage and execution efficiency of TiCDC, TiFlash, and the resolved-ts module of TiKV, and might cause OOM issues. Additionally, BR might be blocked and fail to process when encountering locks. Therefore, it is not recommended to use this mode when these components or features are enabled.

> **Note:**
>
> This variable is read-only for [{{{ .starter }}}](https://docs.pingcap.com/tidbcloud/select-cluster-tier#starter) and [{{{ .essential }}}](https://docs.pingcap.com/tidbcloud/select-cluster-tier#essential).

- Scope: SESSION
- Applies to hint [SET_VAR](/optimizer-hints.md#set_varvar_namevar_value): Yes
- Type: String
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1 change: 1 addition & 0 deletions tidb-cloud/limited-sql-features.md
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Expand Up @@ -142,6 +142,7 @@ TiDB Cloud works with almost all workloads that TiDB supports, but there are som
| `tidb_ddl_reorg_batch_size` | No limitation | Read-only [^10] |
| `tidb_ddl_reorg_priority` | No limitation | Read-only [^10] |
| `tidb_ddl_reorg_worker_cnt` | No limitation | Read-only [^10] |
| `tidb_dml_type` | No limitation | Read-only [^10] |
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medium

This correctly adds the limitation for tidb_dml_type. To ensure documentation completeness and consistency, please also add a note in system-variables.md indicating that this variable is read-only for TiDB Cloud Starter and Essential clusters. This helps users who might only read that document and avoids potential confusion.

References
  1. The style guide emphasizes completeness in documentation (line 14). A corresponding note in system-variables.md is needed to make the documentation about this limitation complete. (link)
  2. The style guide suggests making changes if something might confuse a new user (line 63). The lack of a note in system-variables.md could be confusing. (link)

| `tidb_enable_1pc` | No limitation | Read-only [^10] |
| `tidb_enable_async_commit` | No limitation | Read-only [^10] |
| `tidb_enable_auto_analyze` | No limitation | Read-only [^10] |
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