loader: move loader faq to loader overview

TOC.md

@@ -146,6 +146,7 @@
     + [BR Use Cases](/br/backup-and-restore-use-cases.md)
   + TiDB Binlog
     + [Overview](/tidb-binlog/tidb-binlog-overview.md)
+    + [Quick Start](/tidb-binlog/get-started-with-tidb-binlog.md)
     + [Deploy](/tidb-binlog/deploy-tidb-binlog.md)
     + [Maintain](/tidb-binlog/maintain-tidb-binlog-cluster.md)
     + [Configure](/tidb-binlog/tidb-binlog-configuration-file.md)

loader-overview.md

@@ -1,11 +1,15 @@
 ---
 title: Loader Instructions
 summary: Use Loader to load data to TiDB.
-aliases: ['/docs/dev/loader-overview/','/docs/dev/reference/tools/loader/']
+aliases: ['/docs/dev/loader-overview/','/docs/dev/reference/tools/loader/','/docs/dev/load-misuse-handling/','/docs/dev/reference/tools/error-case-handling/load-misuse-handling/','/tidb/dev/load-misuse-handling']
 ---
 
 # Loader Instructions
 
+> **Warning:**
+>
+> Loader is no longer maintained. Its features are completely superseded by [TiDB Lightning TiDB-backend](/tidb-lightning/tidb-lightning-tidb-backend.md). It is strongly recommend to use TiDB Lightning instead.
+
 ## What is Loader?
 
 Loader is a data import tool to load data to TiDB.
@@ -18,11 +22,11 @@ Since tools like mysqldump will take us days to migrate massive amounts of data,
 
 ## What can Loader do?
 
-+ Multi-thread import data
++ Multi-threaded data import
 
-+ Support table level concurrent import and scattered hot spot write
++ Support table-level concurrent import and scattered hotspot write
 
-+ Support concurrent import of a single large table and scattered hot spot write
++ Support concurrent import of a single large table and scattered hotspot write
 
 + Support Mydumper data format
 
@@ -56,23 +60,23 @@ Since tools like mysqldump will take us days to migrate massive amounts of data,
 
   -d string: the storage directory of data that need to import (default: "./")
 
-  -h string: the host of TiDB (default: "127.0.0.1")
+  -h string: the host IP of TiDB (default: "127.0.0.1")
 
   -p string: the account and password of TiDB
 
   -status-addr string: It can be used by Prometheus to pull Loader metrics, and is also the pprof address of Loader (default: ":8272")
 
-  -t int: the number of thread,increase this as TiKV nodes increase (default: 16)
+  -t int: the number of threads. Each worker restores one file at a time. (default: 16)
 
   -u string: the user name of TiDB (default: "root")
 ```
 
 ### Configuration file
 
-Apart from command line parameters, you can also use configuration files. The format is shown as below:
+Apart from command-line parameters, you can also use configuration files. The format is shown as below:
 
 ```toml
-# Loader log level, which can be set as "debug", "info", "warn", "error" and "fatal" (default: "info")
+# Loader log level, which can be set as "debug", "info", "warn", "error", and "fatal" (default: "info")
 log-level = "info"
 
 # Loader log file
@@ -87,7 +91,7 @@ status-addr = ":8272"
 # The checkpoint data is saved to TiDB, and the schema name is defined here.
 checkpoint-schema = "tidb_loader"
 
-# Number of threads restoring concurrently for worker pool (default: 16). Each worker restore one file at a time.
+# Number of threads restoring concurrently for worker pool (default: 16). Each worker restores one file at a time.
 pool-size = 16
 
 # The target database information
@@ -150,3 +154,36 @@ pattern-table = "table_*"
 target-schema = "example_db"
 target-table = "table"
 ```
+
+## Error: ```Try adjusting the `max_allowed_packet` variable```
+
+The following error is reported during full data import:
+
+```
+packet for query is too large. Try adjusting the 'max_allowed_packet' variable
+```
+
+### Reasons
+
+* Both MySQL client and MySQL/TiDB Server have `max_allowed_packet` quotas. If any of the `max_allowed_packet` quotas is violated, the client receives a corresponding error message. Currently, the latest version of Loader and TiDB Server all have a default `max_allowed_packet` quota of `64M`.
+    * Please use the latest version, or the latest stable version of the tool. See the [download page](/download-ecosystem-tools.md).
+* The full data import processing module in Loader or DM does not support splitting `dump sqls` files. This is because Mydumper has the simple code implementation, as shown in the code comment `/* Poor man's data dump code */`. To support correctly splitting `dump sqls` files, you need to implement a sound parser based on TiDB parser, but you will encounter the following issues:
+    * A large amount of workload.
+    * The task is difficult. It is not easy to ensure the correctness.
+    * Significant performance reduction.
+
+### Solutions
+
+* For the above reasons, it is recommended to use the `-s, --statement-size` option which Mydumper offers to control the size of `Insert Statement`: `Attempted size of INSERT statement in bytes, default 1000000`.
+
+    According to the default configuration of `--statement-size`, the size of `Insert Statement` that Mydumper generates is as close as `1M`. This default configuration ensures that this error will not occur in most cases.
+
+    Sometimes the following `WARN` log appears during the dump process. The `WARN` log itself does not affect the dump process but indicates that the dumped table might be a wide table.
+
+    ```
+    Row bigger than statement_size for xxx
+    ```
+
+* If a single row of a wide table exceeds 64M, you need to modify and enable the following two configurations:
+    * Execute `set @@global.max_allowed_packet=134217728` (`134217728 = 128M`) in TiDB Server.
+    * Add `max-allowed-packet=128M` to db configuration in the Loader configuration file according to your situation, and then restart the progress or task.