DOCS-3699: Warnings around notablescan

Signed-off-by: kay <kay.kim@10gen.com>

source/includes/options-mongod.yaml

@@ -608,7 +608,7 @@ name: notablescan
 args: null
 directive: option
 description: |
-  Forbids operations that require a table scan.
+  Forbids operations that require a table scan. See :parameter:`notablescan` for additional information.
 optional: true
 ---
 program: mongod

source/reference/parameters.txt

@@ -103,16 +103,32 @@ Parameters
 
 .. parameter:: notablescan
 
-   Specify whether queries must use indexes. If ``1``, queries that
-   perform a table scan instead of using an index will fail.
+   Specify whether **all** queries must use indexes. If ``1``, MongoDB
+   will not execute queries that require a table scan and will return an
+   error.
 
-   Consider the following example which sets :parameter:`notablescan` to
-   true:
+   Consider the following example which sets :parameter:`notablescan` to ``1``
+   or true:
 
    .. code-block:: javascript
 
       db.getSiblingDB("admin").runCommand( { setParameter: 1, notablescan: 1 } )
 
+   Setting :parameter:`notablescan` to ``1`` can be useful for testing
+   application queries, for example, to identify queries that scan an
+   entire collection and cannot use an index.
+
+   To detect unindexed queries without ``notablescan``, consider reading
+   the :doc:`/tutorial/evaluate-operation-performance` and
+   :doc:`/tutorial/optimize-query-performance-with-indexes-and-projections`
+   sections and using the :parameter:`logLevel` parameter,
+   :doc:`/reference/program/mongostat` and :ref:`profiling
+   <database-profiling>`.
+
+   Don't run production :program:`mongod` instances with
+   :parameter:`notablescan` because preventing table scans can potentially
+   affect queries in all databases, including administrative queries.
+
 .. parameter:: replIndexPrefetch
 
    .. versionadded:: 2.2