Restore Legacy Database Management doc

Change I6d67e7a40e16468bb7bf4ac742361fb44eec4e28 incorrectly deleted
a document that's required for operators who haven't yet upgraded to
Ocata and are therefore still using the SQLAlchemy Migrate version of
the glance-manage tool.  This patch restores the file.

Change-Id: I821fab32bffb2777a7a7c9e9d8f00ad0813bae64

doc/source/db-sqlalchemy-migrate.rst

@@ -0,0 +1,65 @@
+..
+      Copyright 2012 OpenStack Foundation
+      All Rights Reserved.
+
+      Licensed under the Apache License, Version 2.0 (the "License"); you may
+      not use this file except in compliance with the License. You may obtain
+      a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+      License for the specific language governing permissions and limitations
+      under the License.
+
+Legacy Database Management
+==========================
+
+.. note::
+   This page applies only to Glance releases prior to Ocata.  From Ocata
+   onward, please see :doc:`db`.
+
+The default metadata driver for Glance uses sqlalchemy, which implies there
+exists a backend database which must be managed. The ``glance-manage`` binary
+provides a set of commands for making this easier.
+
+The commands should be executed as a subcommand of 'db':
+
+    glance-manage db <cmd> <args>
+
+
+Sync the Database
+-----------------
+
+    glance-manage db sync <version> <current_version>
+
+Place a database under migration control and upgrade, creating it first if necessary.
+
+
+Determining the Database Version
+--------------------------------
+
+    glance-manage db version
+
+This will print the current migration level of a Glance database.
+
+
+Upgrading an Existing Database
+------------------------------
+
+    glance-manage db upgrade <VERSION>
+
+This will take an existing database and upgrade it to the specified VERSION.
+
+
+Downgrading an Existing Database
+--------------------------------
+
+Upgrades involve complex operations and can fail. Before attempting any
+upgrade, you should make a full database backup of your production data. As of
+Kilo, database downgrades are not supported, and the only method available to
+get back to a prior database version is to restore from backup[1].
+
+[1]: http://docs.openstack.org/ops-guide/ops-upgrades.html#perform-a-backup