(DOCSP-20521): Add example command to modify minSnapshots paraam (#400)

Author: jeff-allen-mongo

source/tutorial/long-running-queries.txt

@@ -166,6 +166,15 @@ the snapshot retention period. To specify how long WiredTiger keeps the
 snapshot history, modify the
 :parameter:`minSnapshotHistoryWindowInSeconds` parameter.
 
+.. example::
+
+   The following command sets ``minSnapshotHistoryWindowInSeconds`` to
+   ``600`` seconds:
+
+   .. code-block:: javascript
+
+      db.adminCommand( { setParameter: 1, minSnapshotHistoryWindowInSeconds: 600 } )
+
 Increasing the value of :parameter:`minSnapshotHistoryWindowInSeconds`
 increases disk usage because the server must maintain the history of
 older modified values within the specified time window. The amount of