diff --git a/.gitignore b/.gitignore
index 486603e..d964a1f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,4 @@ pkg
 *.gem
 *.gemspec
 rdoc
+*.rbc
diff --git a/lib/sbdb/db.rb b/lib/sbdb/db.rb
index 2da1a94..2a0d04a 100644
--- a/lib/sbdb/db.rb
+++ b/lib/sbdb/db.rb
@@ -60,7 +60,11 @@ module SBDB
 
 		def _txn txn
 			txn ||= @txn
-			txn && t.bdb_object
+			txn && txn.bdb_object
+		end
+
+		def transaction flg = nil, &exe
+			block_given? ? home.transaction( flg, &exe) : home.transaction( flg)
 		end
 
 		# Arguments:
diff --git a/lib/sbdb/environment.rb b/lib/sbdb/environment.rb
index 9a6479e..0e2011b 100644
--- a/lib/sbdb/environment.rb
+++ b/lib/sbdb/environment.rb
@@ -61,7 +61,7 @@ module SBDB
 		def initialize *args
 			opts = ::Hash === args.last ? args.pop : {}
 			opts = {:dir => args[0], :flags => args[1], :mode => args[2]}.update opts
-			@dbs, @env = WeakHash.new, Bdb::Env.new( 0)
+			@dbs, @env = Ref::WeakValueMap.new, Bdb::Env.new( 0)
 			@env.log_config opts[:log_config], 1  if opts[:log_config]
 			@env.lg_bsize = opts[:lg_bsize]  if opts[:lg_bsize]
 			@env.lg_max = opts[:lg_max]  if opts[:lg_max]
diff --git a/lib/sbdb/weakhash.rb b/lib/sbdb/weakhash.rb
deleted file mode 100644
index f6e9d9c..0000000
--- a/lib/sbdb/weakhash.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-module SBDB
-
-# See http://eigenclass.org/hiki/deferred-finalizers-in-Ruby
-# Not threadsafe.
-
-class WeakHash
-	attr_reader :cache
-	def initialize cache = ::Hash.new
-		@cache = cache
-		@key_map = {}
-		@rev_cache = ::Hash.new{|h,k| h[k] = {}}
-		@reclaim_value = lambda do |value_id| 
-			if @rev_cache.has_key? value_id
-				@rev_cache[value_id].each_key{|key| @cache.delete key}
-				@rev_cache.delete value_id
-			end
-		end
-		@reclaim_key = lambda do |key_id|
-			@cache.delete @key_map.delete(key_id)  if @key_map.has_key? key_id
-		end
-	end
-
-	def []= key, value
-		case key
-		when Fixnum, Symbol, true, false
-			key2 = key
-		else
-			key2 = key.dup
-		end
-		@rev_cache[value.object_id][key2] = true
-		@cache[key2] = value.object_id
-		@key_map[key.object_id] = key2
-
-		ObjectSpace.define_finalizer(value, @reclaim_value)
-		ObjectSpace.define_finalizer(key, @reclaim_key)
-		value
-	end
-
-	def [] key
-		value_id = @cache[key]
-		return ObjectSpace._id2ref( value_id)  unless value_id.nil?
-		nil
-	rescue RangeError
-		nil
-	end
-
-	def each &e
-		@cache.each do |k, vid|
-			unless vid.nil?
-				obj = begin
-						ObjectSpace._id2ref vid
-					rescue RangeError
-						next
-					end
-				yield k, obj
-			end
-		end
-	end
-end
-
-end