docs: fix outdated Region size in TiDB Cloud glossary

[doc-claw-bot]

What is changed, added or deleted? (Required)

• Update tidb-cloud/tidb-cloud-glossary.md to use the current default Region size (256 MiB) instead of the outdated 96 MB.
• Keep the change scoped to the glossary entry so it stays consistent with the current TiKV Region default described elsewhere in the docs.

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• master (the latest development version)
• v8.5 (TiDB 8.5 versions)
• v8.4 (TiDB 8.4 versions)
• v8.3 (TiDB 8.3 versions)
• v8.2 (TiDB 8.2 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s):

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

Summary by CodeRabbit

• Documentation
  • Updated the glossary’s default TiDB Region size limit from 96 MB to 256 MiB. The limit remains configurable.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign breezewish for approval. For more information see the Code Review Process.
Please ensure that each of them provides their approval before proceeding.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[coderabbitai]

📝 Walkthrough

Walkthrough

The TiDB Cloud glossary changes the TiDB Region default size limit from 96 MB to 256 MiB. The definition still states that the limit can be configured.

Changes

TiDB Region glossary

Layer / File(s)	Summary
Update Region size definition tidb-cloud/tidb-cloud-glossary.md	The definition changes the stated default size limit to 256 MiB and retains the configurability statement.

Priority: ⬇️ Low

Estimated code review effort: 1 (Trivial) | ~2 minutes

Change: Other

Suggested reviewers: qiancai

Merge Risk: 🔵 Low · up to c88d8

The glossary could lead readers to confuse the 256 MiB split target with the higher split threshold. Correcting this localized documentation error is advisable; runtime configuration is unchanged.

Architecture Summary

Architecture risk: 🔵 Low · up to c88d8

The change affects 1 system.

Changed systems: tidb-cloud

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — tidb-cloud (service) was modified; 1 changed file maps to changed impact.

Before / after behavior

• observed — Modified behavior in tidb-cloud/tidb-cloud-glossary.md: The TiDB Region definition changes its default size limit from 96 MB to 256 MiB; configurability remains stated.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely identifies the glossary correction to the Region size.
Description check	✅ Passed	The description covers the change, affected TiDB version, related-link section, AI involvement, and change-type checklist. It explains the reason for the update.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

• Autopilot · Keep fixing CodeRabbit findings and required CI, and resolving merge conflicts

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

Actionable comments posted: 1

---

ℹ️ Review info

⚙️ Run configuration

• Configuration used: Repository: pingcap/docs/.coderabbit.yaml
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: 14910a04-49ff-4468-b41a-e7543bf6efe9

📥 Commits

Reviewing files that changed from the base of the PR and between 49ed15d and c88d82b.

📒 Files selected for processing (1)

• tidb-cloud/tidb-cloud-glossary.md

Included review availability: This review used your included allowance. Your plan provides up to 4 included reviews per hour; 2 remain after this review.

[coderabbitai]

🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

Describe 256 MiB as the estimated split target, not the size limit.

region-split-size estimates the size of a newly split Region. The separate region-max-size threshold defaults to region-split-size / 2 * 3—384 MiB when the split size is 256 MiB.

    The basic unit of data in TiDB. TiKV divides the Key-Value space into a series of consecutive Key segments, and each segment is called a Region. The default estimated target size for a newly split Region is 256 MiB and can be configured.