diff --git a/configure-memory-usage.md b/configure-memory-usage.md
index c754c221b270b..cab9f79a53a10 100644
--- a/configure-memory-usage.md
+++ b/configure-memory-usage.md
@@ -100,7 +100,7 @@ The following example constructs a memory-intensive SQL statement that triggers
 
 2. Execute `CREATE TABLE t(a int);` and insert 1000 rows of data.
 
-3. Execute `select * from t t1 join t t1 join t t3 order by t1.a`. This SQL statement outputs one billion records, which consumes a large amount of memory and therefore triggers the alarm.
+3. Execute `select * from t t1 join t t2 join t t3 order by t1.a`. This SQL statement outputs one billion records, which consumes a large amount of memory and therefore triggers the alarm.
 
 4. Check the `tidb.log` file which records the total system memory, current system memory usage, memory usage of the tidb-server instance, and the directory of status files.
 
diff --git a/sql-plan-replayer.md b/sql-plan-replayer.md
index f670f8c762ce3..15ea8c7627bdb 100644
--- a/sql-plan-replayer.md
+++ b/sql-plan-replayer.md
@@ -49,7 +49,11 @@ analyze table t;
 plan replayer dump explain select * from t;
 ```
 
-`PLAN REPLAYER DUMP` packages the table information above into a `ZIP` file and returns the file identifier as the execution result.
+`PLAN REPLAYER DUMP` packages the table information above into a `ZIP` file and returns the file identifier as the execution result. This file is a one-time file. After the file is downloaded, TiDB will delete it.
+
+> **Note:**
+>
+> The `ZIP` file is stored in a TiDB cluster for at most one hour. After one hour, TiDB will delete it.
 
 ```sql
 MySQL [test]> plan replayer dump explain select * from t;
diff --git a/tidb-configuration-file.md b/tidb-configuration-file.md
index 6350a8435a171..56eac73bf104d 100644
--- a/tidb-configuration-file.md
+++ b/tidb-configuration-file.md
@@ -255,7 +255,8 @@ Configuration items related to log files.
 #### `max-size`
 
 - The size limit of the log file.
-- Default value: 300MB
+- Default value: 300
+- Unit: MB
 - The maximum size is 4GB.
 
 #### `max-days`