docs: update transaction mode (#896)

* update transaction mode

* remove tm in setting

Author: adela-bytebase

mintlify/change-database/settings.mdx

@@ -4,21 +4,6 @@ title: Settings
 
 Customize how database changes work in your projects. Navigate to **Project** → **Settings** to access these options.
 
-## Transaction Mode
-
-<Note>
-Supported databases: MySQL, PostgreSQL, Oracle, SQL Server, TiDB, Redshift
-</Note>
-
-By default, Bytebase wraps SQL statements in a transaction for safety - if something goes wrong, changes can be rolled back.
-
-Some DDL statements can't run inside transactions. To disable transaction wrapping, add this comment before your SQL:
-
-```sql
--- txn-mode=off
-ALTER TABLE t ALTER COLUMN a TYPE VARCHAR(255);
-```
-
 ## Postgres Tenant Mode
 
 Perfect for multi-tenant PostgreSQL setups where each database has its own owner.

mintlify/change-database/transaction-mode.mdx

@@ -0,0 +1,39 @@
+---
+title: Transaction Mode
+---
+
+<Note>
+Supported databases: MySQL, PostgreSQL, Oracle, SQL Server, TiDB, Redshift
+</Note>
+
+Bytebase provides transaction management to ensure safe database changes. By default, all SQL statements are wrapped in a transaction, allowing automatic rollback if errors occur during execution.
+
+## Enable/Disable Transactions
+
+When creating a plan, you can control whether SQL statements are executed within a transaction:
+
+- **Enabled (default)**: All statements run within a transaction boundary for safety
+- **Disabled**: Statements execute directly without transaction wrapping
+
+![Transaction mode toggle](/content/docs/change-database/transaction-mode/bb-transaction-mode.webp)
+
+## MySQL-Specific Settings
+
+For MySQL databases, Bytebase offers additional control over transaction isolation levels to manage concurrent access and data consistency:
+
+![MySQL transaction isolation levels](/content/docs/change-database/transaction-mode/bb-transaction-mode-mysql.webp)
+
+### Available Isolation Levels
+
+- **READ UNCOMMITTED**: Lowest isolation, allows dirty reads
+- **READ COMMITTED**: Prevents dirty reads, allows non-repeatable reads
+- **REPEATABLE READ**: Default MySQL isolation, prevents dirty and non-repeatable reads
+- **SERIALIZABLE**: Highest isolation, prevents all phenomena but may impact performance
+
+## Best Practices
+
+- Keep transactions enabled for DDL and DML operations that modify data
+- Consider disabling transactions only for:
+  - Large batch operations that manage their own transaction boundaries
+  - Statements that cannot run within transactions (e.g., certain administrative commands)
+- Choose appropriate isolation levels based on your concurrency requirements and performance needs

mintlify/content/docs/change-database/transaction-mode/bb-transaction-mode-mysql.webp

@@ -95,6 +95,7 @@
                 "group": "Change",
                 "pages": [
                   "change-database/plan",
+                  "change-database/transaction-mode",
                   "change-database/batch-change",
                   "change-database/synchronize-schema",
                   "change-database/online-schema-migration-for-mysql",