DOCS-14619 clarify dropDatabases sharded cluster procedure

Author: andf-mongodb

source/includes/warning-dropDatabase-shardedCluster.rst

@@ -1,34 +1,70 @@
-.. warning::
-
-   Starting in MongoDB 4.2:
-      If you drop a database and create a new database with the same name, you
-      must either:
-      
-      - Restart all :binary:`~bin.mongos` instances and all
-        :binary:`~bin.mongod` shard members (including the secondary
-        members);
-      
-      - Use the :dbcommand:`flushRouterConfig` command on all
-        :binary:`~bin.mongos` instances and all :binary:`~bin.mongod`
-        shard members (including the secondary members) before reading
-        or writing to that database.
-      
-      This ensures that the :binary:`~bin.mongos` and shard instances
-      refresh their metadata cache, including the location of the
-      :ref:`primary shard <primary-shard>` for the new database.
-      
-      Otherwise, the you may miss data on reads, and may not write data to
-      the correct shard. To recover, you must manually intervene.
-      
-   In MongoDB 4.0 and earlier:      
-      If you drop a database and create a new database with the same name, you
-      must either restart all :binary:`~bin.mongos` instances, or use the
-      :dbcommand:`flushRouterConfig` command on all :binary:`~bin.mongos`
-      instances before reading or writing to that database. This 
-      ensures that the :binary:`~bin.mongos` instances refresh their
-      metadata cache, including the location of the :ref:`primary shard
-      <primary-shard>` for the new database. 
-      
-      Otherwise, the you may miss data on reads, and may not write data to
-      the correct shard. To recover, you must manually intervene.
-      
+If you intend to create a new database with the same name as the dropped
+database, you must follow these additional steps for using the
+:dbcommand:`dropDatabase` command, specific to your version of MongoDB:
+
+- For **MongoDB 4.2**, you must:
+
+  #. Run the :dbcommand:`dropDatabase` command on a
+     :binary:`~bin.mongos`.
+
+  #. Once the command successfully completes, run the
+     :dbcommand:`dropDatabase` command once more on a
+     :binary:`~bin.mongos`.
+
+  #. Use the :dbcommand:`flushRouterConfig` command on **all**
+     :binary:`~bin.mongos` instances before reading or writing to that
+     database.
+
+- For **MongoDB 4.0 and earlier**, you must:
+
+  #. Run the :dbcommand:`dropDatabase` command on a
+     :binary:`~bin.mongos`.
+
+  #. Connect to each shard's :term:`primary` and verify that the
+     namespace has been dropped. If it has not, rerun the
+     :dbcommand:`dropDatabase` command again directly from the
+     :term:`primary`.
+
+  #. Connect to a :binary:`~bin.mongos`, switch to the
+     :term:`config database`, and remove any reference to the removed
+     namespace from the ``databases``, ``collections``, ``chunks``,
+     ``tags``, and ``locks`` collections:
+
+     .. code-block:: javascript
+
+        use config
+        db.collections.remove( { _id: /^DATABASE\./ }, {writeConcern: {w: 'majority' }} )
+        db.databases.remove( { _id: "DATABASE" }, {writeConcern: {w: 'majority' }} )
+        db.chunks.remove( { ns: /^DATABASE\./ }, {writeConcern: {w: 'majority' }} )
+        db.tags.remove( { ns: /^DATABASE\./ }, {writeConcern: {w: 'majority' }} )
+        db.locks.remove( { _id: /^DATABASE\./ }, {writeConcern: {w: 'majority' }} )
+
+     Where ``DATABASE`` represents the namespace of the database you
+     just dropped.
+
+  #. Connect to the :term:`primary` of each shard, and remove any
+     reference to the removed namespace from the ``cache.databases``,
+     ``cache.collections``,  and ``cache.chunks.DATABASE.COLLECTION``
+     collections:
+
+     .. code-block:: javascript
+
+        db.getSiblingDB("config").cache.databases.remove({_id:"DATABASE"}, {writeConcern: {w: 'majority' }});
+        db.getSiblingDB("config").cache.collections.remove({_id:/^DATABASE.*/}, {writeConcern: {w: 'majority' }});
+        db.getSiblingDB("config").getCollectionNames().forEach(function(y) {
+           if(y.indexOf("cache.chunks.DATABASE.") == 0)
+            db.getSiblingDB("config").getCollection(y).drop()
+         })
+
+     Where ``DATABASE`` represents the namespace of the database you
+     just dropped.
+
+  #. Use the :dbcommand:`flushRouterConfig` command on **all**
+     :binary:`~bin.mongos` instances before reading or writing to that
+     database.
+
+These steps ensure that all cluster nodes refresh their metadata cache,
+which includes the location of the :ref:`primary shard<primary-shard>`
+for the new database. Otherwise, you may miss data on reads, and may not
+write data to the correct shard. To recover, you must manually
+intervene.

source/reference/command/dropDatabase.txt

@@ -82,7 +82,7 @@ User Management
 Replica Set and Sharded Clusters
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. versionchanged:: 3.6
+.. versionchanged:: 4.2
 
 Replica Sets
    At minimum, :dbcommand:`dropDatabase` waits until all collections