pingcap · ti-chi-bot · Feb 20, 2023 · Feb 20, 2023 · Feb 20, 2023
diff --git a/TOC.md b/TOC.md
@@ -4,7 +4,7 @@
 - [Docs Home](https://docs.pingcap.com/)
 - About TiDB
   - [TiDB Introduction](/overview.md)
-  - [TiDB 6.5 Release Notes](/releases/release-6.5.0.md)
+  - [TiDB 6.6 Release Notes](/releases/release-6.6.0.md)
   - [Features](/basic-features.md)
   - [MySQL Compatibility](/mysql-compatibility.md)
   - [TiDB Limitations](/tidb-limitations.md)
@@ -939,6 +939,8 @@
   - [Release Timeline](/releases/release-timeline.md)
   - [TiDB Versioning](/releases/versioning.md)
   - [TiDB Installation Packages](/binary-package.md)
+  - v6.6
+    - [6.6.0](/releases/release-6.6.0.md)
   - v6.5
     - [6.5.0](/releases/release-6.5.0.md)
   - v6.4

diff --git a/_index.md b/_index.md
@@ -70,9 +70,13 @@ hide_commit: true
 
 [Scale a Cluster](https://docs.pingcap.com/tidb/v6.6/scale-tidb-using-tiup)
 
+<<<<<<< HEAD
 [Back Up and Restore Cluster Data](https://docs.pingcap.com/tidb/v6.6/backup-and-restore-overview)
 
 [Daily Check](https://docs.pingcap.com/tidb/v6.6/daily-check)
+=======
+[Back Up and Restore Cluster Data](https://docs.pingcap.com/tidb/dev/backup-and-restore-overview)
+>>>>>>> b36425063 (add 6.6.0 release notes (#12321))
 
 [Maintain TiDB Using TiUP](https://docs.pingcap.com/tidb/v6.6/maintain-tidb-using-tiup)
 

diff --git a/releases/release-6.6.0.md b/releases/release-6.6.0.md
diff --git a/releases/release-notes.md b/releases/release-notes.md
@@ -4,6 +4,10 @@ title: Release Notes
 
 # TiDB Release Notes
 
+## 6.6
+
+- [6.6.0](/releases/release-6.6.0.md): 2023-02-20
+
 ## 6.5
 
 - [6.5.0](/releases/release-6.5.0.md): 2022-12-29

diff --git a/releases/release-timeline.md b/releases/release-timeline.md
@@ -9,6 +9,7 @@ This document shows all the released TiDB versions in reverse chronological orde
 
 | Version | Release Date |
 | :--- | :--- |
+| [6.6.0](/releases/release-6.6.0.md) | 2023-02-20 |
 | [6.1.4](/releases/release-6.1.4.md) | 2023-02-08 |
 | [6.5.0](/releases/release-6.5.0.md) | 2022-12-29 |
 | [5.1.5](/releases/release-5.1.5.md) | 2022-12-28 |

diff --git a/sql-statements/sql-statement-flashback-to-timestamp.md b/sql-statements/sql-statement-flashback-to-timestamp.md
@@ -40,13 +40,29 @@ FlashbackToTimestampStmt ::=
     SELECT * FROM mysql.tidb WHERE variable_name = 'tikv_gc_safe_point';
     ```
 
+<CustomContent platform='tidb'>
+
 * Only a user with the `SUPER` privilege can execute the `FLASHBACK CLUSTER` SQL statement.
 * `FLASHBACK CLUSTER` does not support rolling back DDL statements that modify PD-related information, such as `ALTER TABLE ATTRIBUTE`, `ALTER TABLE REPLICA`, and `CREATE PLACEMENT POLICY`.
 * At the time specified in the `FLASHBACK` statement, there cannot be a DDL statement that is not completely executed. If such a DDL exists, TiDB will reject it.
 * Before executing `FLASHBACK CLUSTER TO TIMESTAMP`, TiDB disconnects all related connections and prohibits read and write operations on these tables until the `FLASHBACK CLUSTER` statement is completed.
 * The `FLASHBACK CLUSTER TO TIMESTAMP` statement cannot be canceled after being executed. TiDB will keep retrying until it succeeds.
+* During the execution of `FLASHBACK CLUSTER`, if you need to back up data, you can only use [Backup & Restore](/br/br-snapshot-guide.md) and specify a `BackupTS` that is earlier than the start time of `FLASHBACK CLUSTER`. In addition, during the execution of `FLASHBACK CLUSTER`, enabling [log backup](/br/br-pitr-guide.md) will fail. Therefore, try to enable log backup after `FLASHBACK CLUSTER` is completed.
 * If the `FLASHBACK CLUSTER` statement causes the rollback of metadata (table structure, database structure), the related modifications will **not** be replicated by TiCDC. Therefore, you need to pause the task manually, wait for the completion of `FLASHBACK CLUSTER`, and manually replicate the schema definitions of the upstream and downstream to make sure that they are consistent. After that, you need to recreate the TiCDC changefeed.
 
+</CustomContent>
+
+<CustomContent platform='tidb-cloud'>
+
+* Only a user with the `SUPER` privilege can execute the `FLASHBACK CLUSTER` SQL statement.
+* `FLASHBACK CLUSTER` does not support rolling back DDL statements that modify PD-related information, such as `ALTER TABLE ATTRIBUTE`, `ALTER TABLE REPLICA`, and `CREATE PLACEMENT POLICY`.
+* At the time specified in the `FLASHBACK` statement, there cannot be a DDL statement that is not completely executed. If such a DDL exists, TiDB will reject it.
+* Before executing `FLASHBACK CLUSTER TO TIMESTAMP`, TiDB disconnects all related connections and prohibits read and write operations on these tables until the `FLASHBACK CLUSTER` statement is completed.
+* The `FLASHBACK CLUSTER TO TIMESTAMP` statement cannot be canceled after being executed. TiDB will keep retrying until it succeeds.
+* If the `FLASHBACK CLUSTER` statement causes the rollback of metadata (table structure, database structure), the related modifications will **not** be replicated by TiCDC. Therefore, you need to pause the task manually, wait for the completion of `FLASHBACK CLUSTER`, and manually replicate the schema definitions of the upstream and downstream to make sure that they are consistent. After that, you need to recreate the TiCDC changefeed.
+
+</CustomContent>
+
 ## Example
 
 The following example shows how to restore the newly inserted data:

diff --git a/system-variables.md b/system-variables.md
@@ -1534,16 +1534,20 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a
 - Scope: GLOBAL
 - Persists to cluster: Yes
 - Type: Boolean
-- Default value: `OFF`
-- This variable is used for an unreleased feature. **Do not change the variable value**.
+- Default value: `ON`
+- This variable controls whether to enable historical statistics. The default value changes from `OFF` to `ON`, which means that historical statistics are enabled by default.
 
-### `tidb_enable_historical_stats_for_capture`
+### tidb_enable_historical_stats_for_capture
+
+> **Warning:**
+>
+> The feature controlled by this variable is not fully functional in the current TiDB version. Do not change the default value.
 
 - Scope: GLOBAL
 - Persists to cluster: Yes
 - Type: Boolean
 - Default value: `OFF`
-- This variable is used for an unreleased feature. **Do not change the variable value**.
+- This variable controls whether the information captured by `PLAN REPLAYER CAPTURE` includes historical statistics by default. The default value `OFF` means that historical statistics are not included by default.
 
 ### tidb_enable_index_merge <span class="version-mark">New in v4.0</span>
 
@@ -1748,8 +1752,8 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a
 - Scope: SESSION | GLOBAL
 - Persists to cluster: Yes
 - Type: Boolean
-- Default value: `OFF`
-- This variable controls whether to enable the [`PLAN REPLAYER CAPTURE` feature](/sql-plan-replayer.md#use-plan-replayer-capture-to-capture-target-plans). The default value `OFF` means to disable the `PLAN REPLAYER CAPTURE` feature.
+- Default value: `ON`
+- This variable controls whether to enable the [`PLAN REPLAYER CAPTURE` feature](/sql-plan-replayer.md#use-plan-replayer-capture-to-capture-target-plans). The default value `ON` means to enable the `PLAN REPLAYER CAPTURE` feature.
 
 </CustomContent>
 

diff --git a/tikv-configuration-file.md b/tikv-configuration-file.md
@@ -1261,7 +1261,11 @@ Configuration items related to `rocksdb.defaultcf`, `rocksdb.writecf`, and `rock
 
 ### `block-cache-size`
 
-+ The cache size of a RocksDB block. Starting from v6.6.0, this configuration is only used to calculate the default value of `storage.block-cache.capacity`.
+> **Warning:**
+>
+> Starting from v6.6.0, this configuration is deprecated.
+
++ The cache size of a RocksDB block.
 + Default value for `defaultcf`: `Total machine memory * 25%`
 + Default value for `writecf`: `Total machine memory * 15%`
 + Default value for `lockcf`: `Total machine memory * 2%`

diff --git a/upgrade-tidb-using-tiup.md b/upgrade-tidb-using-tiup.md
@@ -47,7 +47,7 @@ This section introduces the preparation works needed before upgrading your TiDB
 
 ### Step 1: Review compatibility changes
 
-Review [the compatibility changes](/releases/release-6.5.0.md#compatibility-changes) and [deprecated features](/releases/release-6.5.0.md#deprecated-feature) in TiDB v6.5.0 release notes. If any changes affect your upgrade, take actions accordingly.
+Review [the compatibility changes](/releases/release-6.6.0.md#compatibility-changes) in TiDB v6.6.0 release notes. If any changes affect your upgrade, take actions accordingly.
 
 ### Step 2: Upgrade TiUP or TiUP offline mirror