tools: update DM TOC and refine content (pingcap#869)

* tools: update DM TOC and refine content

* readme: update DM Deploy link

README.md

@@ -123,19 +123,25 @@
   - [mydumper](tools/mydumper.md)
   - [Loader](tools/loader.md)
   + Data Migration
-    + Overview
-      - [Architecture](tools/data-migration-overview.md#architecture)
-      - [Features](tools/data-migration-overview.md#data-synchronization-introduction)
-      - [Restrictions](tools/data-migration-overview.md#usage-restrictions)
-    - [Deploy](tools/data-migration-deployment.md)
-    - [Synchronize Data](tools/data-migration-practice.md)
+    - [Overview](tools/data-migration-overview.md)
+    - [Restrictions](tools/data-migration-overview.md#usage-restrictions)
+    + Features
+      - [Table Routing](tools/dm-data-synchronization-features.md#table-routing)
+      - [Black and White Lists](tools/dm-data-synchronization-features.md#black-and-white-table-lists)
+      - [Binlog Event Filtering](tools/dm-data-synchronization-features.md#binlog-event-filtering)
+      - [Column Mapping](tools/dm-data-synchronization-features.md#column-mapping)
+      - [Synchronization Delay Monitoring](tools/dm-data-synchronization-features.md#synchronization-delay-monitoring)
+      + Sharding Support
+        - [Introduction](tools/dm-sharding-solution.md)
+        - [Restrictions](tools/dm-sharding-solution.md#sharding-ddl-usage-restrictions)
+        - [Troubleshoot](tools/troubleshooting-sharding-ddl-locks.md)
+    + Usage Scenarios
+      - [Simple Scenario](tools/dm-simple-synchronization-scenario.md)
+      - [Shard Merge Scenario](tools/dm-shard-merge-scenario.md)
+    - [Deploy](tools/data-migration-practice.md)
     + Configure
-      - [Configuration Overview](tools/dm-configuration-file-overview.md)
-      - [Task Configuration File](tools/dm-task-configuration-file-intro.md)
-    + Sharding Data Solution
-      - [Overview and Design Details](tools/dm-sharding-solution.md)
-      - [Sharding DDL Usage Restrictions](tools/dm-sharding-solution.md#sharding-ddl-usage-restrictions)
-      - [Troubleshoot Sharding DDL Locks](tools/troubleshooting-sharding-ddl-locks.md)
+      - [Overview](tools/dm-configuration-file-overview.md)
+      - [Task Configuration](tools/dm-task-configuration-file-intro.md)
     - [Monitor](tools/dm-monitor.md)
     - [Manage the Task](tools/data-migration-manage-task.md)
     - [Cluster Operations](tools/data-migration-cluster-operations.md)

tools/data-migration-manage-task.md

@@ -88,6 +88,11 @@ To detect possible errors of data synchronization configuration in advance, DM p
 
 The user of the upstream and downstream databases must have the corresponding read and write privileges. DM checks the following privileges and configuration automatically while starting the data synchronization task:
 
++ Database version
+
+    - 5.5 < MySQL version < 5.8
+    - MariaDB version >= 10.1.2
+
 + MySQL binlog configuration
 
     - Whether the binlog is enabled (DM requires that the binlog must be enabled)
@@ -193,7 +198,7 @@ start-task [ -w "172.16.30.15:10081"] ./task.yaml
 
 ### Check the data synchronization task status
 
-You can use the task management command to check the status of the data synchronization task.
+You can use the `query-status` task management command to check the status of the data synchronization task. For details about the query result and subtask status, see [Query Status](../tools/dm-query-status.md).
 
 ```bash
 » help query-status

tools/data-migration-overview.md

@@ -33,7 +33,7 @@ DM-worker executes specific data synchronization tasks.
 - Orchestrating the operation of the data synchronization subtasks
 - Monitoring the running state of the data synchronization subtasks
 
-For details about DM-worker, see [DM-worker Introduction](../tools/dm-worker-intro.md).
+After DM-worker is started, it automatically synchronizes the upstream binlog to the local configuration directory (the default synchronization directory is `<deploy_dir>/relay_log` if DM is deployed using `DM-Ansible`). For details about DM-worker, see [DM-worker Introduction](../tools/dm-worker-intro.md). For details about the relay log, see [Relay Log](../tools/dm-relay-log.md).
 
 ### dmctl 
 

tools/data-migration-practice.md

@@ -104,6 +104,10 @@ mydumpers:
 
 ## Step 4: Start the data synchronization task
 
+> **Note:**
+> 
+> To detect possible errors of data synchronization configuration in advance, DM provides the precheck feature. DM automatically checks the corresponding privileges and configuration while starting the data synchronization task. You can also use the `check-task` command to manually precheck whether the upstream MySQL instance configuration satisfies the DM requirements. For details about the precheck feature, see [Precheck the upstream MySQL instance configuration](../tools/data-migration-manage-task.md#precheck-the-upstream-mysql-instance-configuration).
+
 1. Come to the dmctl directory `/home/tidb/dm-ansible/resource/bin/`.
 
 2. Run the following command to start dmctl.