tidb-configuration-file: add more notes to txn-entry-size-limit (#10629)

tidb-configuration-file.md

@@ -362,6 +362,8 @@ Configuration items related to performance.
 - Default value: `6291456` (in bytes)
 - The size limit of a single key-value record in a transaction. If the size limit is exceeded, TiDB returns the `entry too large` error. The maximum value of this configuration item does not exceed `125829120` (120 MB).
 - Note that TiKV has a similar limit. If the data size of a single write request exceeds [`raft-entry-max-size`](/tikv-configuration-file.md#raft-entry-max-size), which is 8 MB by default, TiKV refuses to process this request. When a table has a row of large size, you need to modify both configurations at the same time.
+- The default value of [`max_allowed_packet`](/system-variables.md#max_allowed_packet-new-in-v610) (the maximum size of a packet for the MySQL protocol) is 67108864 (64 MiB). If a row is larger than `max_allowed_packet`, the row gets truncated.
+- The default value of [`txn-total-size-limit`](#txn-total-size-limit) (the size limit of a single transaction in TiDB) is 100 MiB. If you increase the `txn-entry-size-limit` value to be over 100 MiB, you need to increase the `txn-total-size-limit` value accordingly.
 
 ### `txn-total-size-limit`
 

tidb-limitations.md

@@ -53,9 +53,9 @@ This document describes the common usage limitations of TiDB, including the maxi
 
 ## Limitation on a single row
 
-| Type       | Upper limit   |
+| Type       | Upper limit (default value)   |
 |:----------|:----------|
-| Size       | 6 MB  |
+| Size       | Defaults to 6 MiB and can be adjusted to 120 MiB  |
 
 <CustomContent platform="tidb">
 
@@ -65,20 +65,26 @@ You can adjust the size limit via the [`txn-entry-size-limit`](/tidb-configurati
 
 ## Limitation on a single column
 
-| Type       | Upper limit   |
+| Type       | Upper limit (default value)   |
 |:----------|:----------|
-| Size       | 6 MB       |
+| Size       | Defaults to 6 MiB and can be adjusted to 120 MiB  |
+
+<CustomContent platform="tidb">
+
+You can adjust the size limit via the [`txn-entry-size-limit`](/tidb-configuration-file.md#txn-entry-size-limit-new-in-v50) configuration item.
+
+</CustomContent>
 
-## Limitations on string types
+## Limitations on data types
 
 | Type       | Upper limit   |
 |:----------|:----------|
 | CHAR       | 256 characters      |
 | BINARY     | 256 characters      |
 | VARBINARY  | 65535 characters    |
 | VARCHAR    | 16383 characters    |
-| TEXT       | 6 MB                |
-| BLOB       | 6 MB                |
+| TEXT       | Defaults to 6 MiB and can be adjusted to 120 MiB                |
+| BLOB       | Defaults to 6 MiB and can be adjusted to 120 MiB               |
 
 ## Limitations on SQL statements