DOCS-267 power of two sizes documentation

Author: Sam Kleinman

source/reference/collection-statistics.txt

@@ -102,9 +102,31 @@ Fields
 
 .. stats:: flags
 
-   Indicates the number of flags on the current collection. At the
-   preset, the only flag notes the existence of an :term:`index` on
-   the :term:`_id` field.
+   .. versionchanged:: 2.2
+      Removed in version 2.2 and replaced with the :stats:`userFlags`
+      and :stats:`systemFlags` fields.
+
+   Indicates the number of flags on the current collection. In version
+   2.0, the only flag notes the existence of an :term:`index` on the
+   :term:`_id` field.
+
+.. stats:: systemFlags
+
+   .. versionadded:: 2.2
+
+   Reports the number of flags on this collection that reflect
+   internal server activity. Typically this value is ``1`` and
+   reflects the existence of an :term:`index` on the ``_id`` field.
+
+.. stats:: userFlags
+
+   .. versionadded:: 2.2
+
+   Reports the total number of flags on this collection that reflect
+   user actions. In version 2.2 the only user collection flag is
+   ``usePowerOf2Sizes``. See :dbcommand:`collMod`` for more
+   information on setting user flags and :ref:`usePowerOf2Sizes
+   <usePowerOf2Sizes>`.
 
 .. stats:: totalIndexSize
 

source/reference/commands.txt

@@ -1212,6 +1212,37 @@ Collections
    - It is not possible to compact :term:`capped collections <capped
      collection>`.
 
+.. dbcommand:: collMod
+
+   .. versionadded:: 2.2
+
+   :dbcommand:`collMod` makes it possible to add flags to a collection
+   to modify the behavior of MongoDB. In the current release the only
+   available flag is ``usePowerof2Sizes``. The command takes the
+   following prototype form:
+
+   .. code-block:: javascript
+
+      db.runCommand( {"collMod" : [collection] , "[flag]" : [value]" } )
+
+   In this command substitute ``[collection]`` with the name of the
+   collection, and ``[flag]`` and ``[value]`` with the flag and value
+   you want to set.
+
+   .. index:: usePowerOf2Sizes
+   .. _usePowerOf2Sizes:
+
+   The ``usePowerOf2Sizes`` flag changes the method that MongoDB uses
+   to allocate space on disk for documents in this collection. By
+   setting ``usePowerOf2Sizes``, you ensure that MongoDB will
+   allocates space for documents in sizes that are powers of 2
+   (e.g. 4, 8, 16, 32, 64, 128, 512...) With this option MongoDB will
+   be able to more effectively reuse space.
+
+   ``usePowerOf2Sizes`` is useful for collection where you will be
+   inserting and deleting large numbers of documents to ensure that
+   MongoDB will effectively use space on disk.
+
 Administration
 ~~~~~~~~~~~~~~