clarify lightning post-restore description (#9433)

Author: ran-huang

tidb-lightning/tidb-lightning-configuration.md

@@ -400,11 +400,11 @@ max-allowed-packet = 67_108_864
 # Private key of this service. Default to copy of `security.key-path`
 # key-path = "/path/to/lightning.key"
 
-# In the physical import mode, when data importing is complete, tidb-lightning can
+# In the physical import mode, when data importing is complete, TiDB Lightning can
 # automatically perform the Checksum and Analyze operations. It is recommended
 # to leave these as true in the production environment.
 # The execution order: Checksum -> Analyze.
-# In the logical import mode, Checksum and Analyze is not needed, and they are always
+# Note that in the logical import mode, Checksum and Analyze is not needed, and they are always
 # skipped in the actual operation.
 [post-restore]
 # Specifies whether to perform `ADMIN CHECKSUM TABLE <table>` for each table to verify data integrity after importing.
@@ -413,7 +413,9 @@ max-allowed-packet = 67_108_864
 # - "optional": Perform admin checksum. If checksum fails, TiDB Lightning will report a WARN log but ignore any error.
 # - "off": Do not perform checksum.
 # Note that since v4.0.8, the default value has changed from "true" to "required".
-# For backward compatibility, bool values "true" and "false" are also allowed for this field.
+# Note:
+# 1. Checksum failure usually means import exception (data loss or inconsistency). It is recommended to always enable checksum.
+# 2. For backward compatibility, bool values "true" and "false" are also allowed for this field.
 # "true" is equivalent to "required" and "false" is equivalent to "off".
 checksum = "required"
 # Specifies whether the ADMIN CHECKSUM TABLE <table> operation is executed via TiDB.
@@ -425,16 +427,6 @@ checksum-via-sql = "false"
 # Options available for this field are the same as `checksum`. However, the default value for this field is "optional".
 analyze = "optional"
 
-# If the value is set to `true`, a level-1 compaction is performed
-# every time a table is imported.
-# The default value is `false`.
-level-1-compact = false
-
-# If the value is set to `true`, a full compaction on the whole
-# TiKV cluster is performed at the end of the import.
-# The default value is `false`.
-compact = false
-
 # Configures the background periodic actions.
 # Supported units: h (hour), m (minute), s (second).
 [cron]