Index: db/migrate/087_change_projects_description_to_text.rb
===================================================================
--- db/migrate/087_change_projects_description_to_text.rb	(revision 18254)
+++ db/migrate/087_change_projects_description_to_text.rb	(working copy)
@@ -1,5 +1,8 @@
 class ChangeProjectsDescriptionToText < ActiveRecord::Migration[4.2]
   def self.up
+    if Redmine::Database.sqlserver?
+      change_column :projects, :description, :text
+    end
     change_column :projects, :description, :text, :null => true, :default => nil
   end
 
Index: db/migrate/20100705164950_change_changes_path_length_limit.rb
===================================================================
--- db/migrate/20100705164950_change_changes_path_length_limit.rb	(revision 18254)
+++ db/migrate/20100705164950_change_changes_path_length_limit.rb	(working copy)
@@ -1,5 +1,8 @@
 class ChangeChangesPathLengthLimit < ActiveRecord::Migration[4.2]
   def self.up
+    if Redmine::Database.sqlserver?
+      change_column :changes, :path, :text
+    end
     # these are two steps to please MySQL 5 on Win32
     change_column :changes, :path, :text, :default => nil, :null => true
     change_column :changes, :path, :text, :null => false
Index: db/migrate/20151020182334_change_attachments_filesize_limit_to_8.rb
===================================================================
--- db/migrate/20151020182334_change_attachments_filesize_limit_to_8.rb	(revision 18254)
+++ db/migrate/20151020182334_change_attachments_filesize_limit_to_8.rb	(working copy)
@@ -1,6 +1,11 @@
 class ChangeAttachmentsFilesizeLimitTo8 < ActiveRecord::Migration[4.2]
   def self.up
-    change_column :attachments, :filesize, :integer, :limit => 8, :default => 0, :null => false
+    if Redmine::Database.sqlserver?
+      change_column :attachments, :filesize, :bigint
+      change_column :attachments, :filesize, :bigint, :limit => 8, :default => 0, :null => false
+    else
+      change_column :attachments, :filesize, :integer, :limit => 8, :default => 0, :null => false
+    end
   end
 
   def self.down
Index: Gemfile
===================================================================
--- Gemfile	(revision 18254)
+++ Gemfile	(working copy)
@@ -59,8 +59,8 @@
       when /sqlite3/
         gem "sqlite3", "~> 1.4.0", :platforms => [:mri, :mingw, :x64_mingw]
       when /sqlserver/
-        gem "tiny_tds", "~> 1.0.5", :platforms => [:mri, :mingw, :x64_mingw]
-        gem "activerecord-sqlserver-adapter", :platforms => [:mri, :mingw, :x64_mingw]
+        gem "tiny_tds", "~> 2.1.2", :platforms => [:mri, :mingw, :x64_mingw]
+        gem "activerecord-sqlserver-adapter", "~> 5.2.0", :platforms => [:mri, :mingw, :x64_mingw]
       else
         warn("Unknown database adapter `#{adapter}` found in config/database.yml, use Gemfile.local to load your own database gems")
       end
Index: lib/redmine/database.rb
===================================================================
--- lib/redmine/database.rb	(revision 18254)
+++ lib/redmine/database.rb	(working copy)
@@ -51,6 +51,11 @@
         /mysql/i.match?(ActiveRecord::Base.connection.adapter_name)
       end
 
+      # Returns true if the database is SQL Server
+      def sqlserver?
+        /sqlserver/i.match?(ActiveRecord::Base.connection.adapter_name)
+      end
+
       # Returns a SQL statement for case/accent (if possible) insensitive match
       def like(left, right, options={})
         neg = (options[:match] == false ? 'NOT ' : '')
Index: lib/redmine/nested_set/issue_nested_set.rb
===================================================================
--- lib/redmine/nested_set/issue_nested_set.rb	(revision 18254)
+++ lib/redmine/nested_set/issue_nested_set.rb	(working copy)
@@ -151,7 +151,7 @@
       end
 
       def lock_nested_set
-        if /sqlserver/i.match?(self.class.connection.adapter_name)
+        if Redmine::Database.sqlserver?
           lock = "WITH (ROWLOCK HOLDLOCK UPDLOCK)"
           # Custom lock for SQLServer
           # This can be problematic if root_id or parent root_id changes
Index: lib/redmine/nested_set/project_nested_set.rb
===================================================================
--- lib/redmine/nested_set/project_nested_set.rb	(revision 18254)
+++ lib/redmine/nested_set/project_nested_set.rb	(working copy)
@@ -121,7 +121,7 @@
 
       def lock_nested_set
         lock = true
-        if /sqlserver/i.match?(self.class.connection.adapter_name)
+        if Redmine::Database.sqlserver?
           lock = "WITH (ROWLOCK HOLDLOCK UPDLOCK)"
         end
         self.class.order(:id).lock(lock).ids