[doc] fix backup doc (#8529)

docs/en/administrator-guide/backup-restore.md

@@ -45,6 +45,14 @@ The backup operation is to upload the data of the specified table or partition d
 2. Metadata preparation and upload
 
 	After the data file snapshot is uploaded, Frontend first writes the corresponding metadata to the local file, and then uploads the local metadata file to the remote warehouse through broker. Finish the final backup job.
+	
+3. Dynamic partition table description
+
+    If the table is a dynamic partition table, the dynamic partition attribute will be automatically disabled after backup. When restoring, you need to manually enable the dynamic partition attribute of the table. The command is as follows:
+
+    ```sql
+    ALTER TABLE tbl1 SET ("dynamic_partition.enable"="true")
+    ````
 
 ### Restore
 

docs/zh-CN/administrator-guide/backup-restore.md

@@ -44,7 +44,14 @@ Doris 支持将当前数据以文件的形式，通过 broker 备份到远端存
 
 2. 元数据准备及上传
 
-    数据文件快照上传完成后，Frontend 会首先将对应元数据写成本地文件，然后通过 broker 将本地元数据文件上传到远端仓库。完成最终备份作业。
+    数据文件快照上传完成后，Frontend 会首先将对应元数据写成本地文件，然后通过 broker 将本地元数据文件上传到远端仓库。完成最终备份作业
+    
+2. 动态分区表说明
+
+    如果该表是动态分区表，备份之后会自动禁用动态分区属性，在做恢复的时候需要手动将该表的动态分区属性启用，命令如下:
+    ```sql
+    ALTER TABLE tbl1 SET ("dynamic_partition.enable"="true")
+    ```
 
 ### 恢复（Restore）