diff --git a/lib/mdb/db.py b/lib/mdb/db.py
index d326710..d675e6a 100644
--- a/lib/mdb/db.py
+++ b/lib/mdb/db.py
@@ -5,7 +5,7 @@
 # itself while defining objects that the database will return.
 #
 
-import rcs, re
+import rcs, os
 
 
 #
@@ -50,11 +50,19 @@ class PVVDB:
     def __init__(self, base):
         # Find the record definition file, read it, verify it and
         # set the legal set of fields.
-        pass
+        self.base  = base               # base database directory
+        self.locks = []                 # list of activated locks
+        self.rcs   = rcs.RCS()          # an RCS interface function
 
     def __del__(self):
         # clean up locks and such before being deleted.
-        pass
+        for username in self.locks:
+            self.rcs.unlock(username)
+
+    def __filename(self, username):
+        # transform the username into a tuple with the full name of
+        # the databasefile and the latest revision number.
+        return self.rcs.rcsname(os.path.join(self.base, username))
 
     def __format(self, file_path):
         # parses and verifies the .format files for a database.
@@ -63,18 +71,22 @@ class PVVDB:
         for line in fh:
             if line[0] == "#":
                 continue
-            name, value    = line.strip().split(":", 1)
-            value          = value.split("#", 1)[0].strip()
+            name, value = line.strip().split(":", 1)
+            value       = value.split("#", 1)[0].strip()
             if not value in ['scalar', 'list']:
                 raise PVVDBError, "%s not legal .format datatype." % value
             fmt[name] = value
         return fmt
 
-    def lock(self, username):
+    def lock(self, username, pedantic=False):
         # Lock the record.
-        pass
+        if username in self.locks and pedantic:
+            raise PVVDBError, "%s already locked." % `username`
+        self.rcs.lock(self.__filename(username))
+        self.locks.append(username)
+        
 
-    def unlock(self, username):
+    def unlock(self, username, pedantic=False):
         # Unlock the record.
         pass