DOCS-4684: changes in limits for wt

Author: Sam Kleinman

source/reference/limits.txt

@@ -32,24 +32,31 @@ Namespaces
    Each namespace, including database and collection name, must be
    shorter than 123 bytes.
 
-   .. fix when we know what the actual limit is.
-
 .. _limit-number-of-namespaces:
 .. limit:: Number of Namespaces
 
-   The limitation on the number of namespaces is the size of the
-   namespace file divided by 628.
+   .. versionchanged:: 3.0
+
+   For the MMAPv1 the number of namespaces is limited to the size of
+   the namespace file divided by 628.
 
    A 16 megabyte namespace file can support approximately 24,000
    namespaces. Each collection and index is a namespace.
 
+   The WiredTiger storage engine is *not* subject to this limitation.
+
 .. _limit-size-of-namespace-file:
 .. limit:: Size of Namespace File
 
-   Namespace files can be no larger than 2047 megabytes.
+   .. versionchanged:: 3.0
+
+   For the MMAPv1 storage engine, namespace files can be no larger
+   than 2047 megabytes.
 
    By default namespace files are 16 megabytes. You can configure the
-   size using the :setting:`~storage.nsSize` option.
+   size using the :setting:`~storage.mmapv1.nsSize` option.
+
+   The WiredTiger storage engine is *not* subject to this limitation.
 
 .. _index-limitations:
 
@@ -128,9 +135,11 @@ Data
 .. _limit-data-size:
 .. limit:: Data Size
 
-   A single :program:`mongod` instance cannot manage a data set that
-   exceeds maximum virtual memory address space provided by the
-   underlying operating system.
+   .. versionchanged:: 3.0
+
+   Using the MMAPv1 storage engine, a single :program:`mongod`
+   instance cannot manage a data set that exceeds maximum virtual
+   memory address space provided by the underlying operating system.
 
    .. list-table:: Virtual Memory Limitations
       :widths: 15 10 10
@@ -149,11 +158,17 @@ Data
         - 4 terabytes
         - 8 terabytes
 
+   The WiredTiger storage engine is *not* subject to this limitation.
+
 .. limit:: Number of Collections in a Database
 
-   The maximum number of collections in a database is a function of
-   the size of the namespace file and the number of indexes of
-   collections in the database.
+   .. versionchanged:: 3.0
+
+   For the MMAPv1 storage engine, the maximum number of collections in
+   a database is a function of the size of the namespace file and the
+   number of indexes of collections in the database.
+
+   The WiredTiger storage engine is *not* subject to this limitation.
 
    See :limit:`Number of Namespaces` for more information.
 
@@ -164,9 +179,9 @@ Replica Sets
 
    .. versionchanged:: 3.0.0
 
-   Replica sets can have up to 50 members; however, not all drivers are
-   suitable for use with large replica sets. For more information, see
-   :ref:`3.0-replica-sets-max-members`.
+   Replica sets can have up to 50 members. See
+   :ref:`3.0-replica-sets-max-members` for more information about
+   specific driver compatibility with large replica sets.
 
 .. limit:: Number of Voting Members of a Replica Set