diff --git a/pyfpdb/fpdb.py b/pyfpdb/fpdb.py
index 379b4e44..8a26462d 100755
--- a/pyfpdb/fpdb.py
+++ b/pyfpdb/fpdb.py
@@ -174,35 +174,36 @@ class fpdb:
 
     def dia_load_profile(self, widget, data=None):
         """Dialogue to select a file to load a profile from"""
-        self.obtain_global_lock()
-        chooser = gtk.FileChooserDialog(title="Please select a profile file to load",
-                action=gtk.FILE_CHOOSER_ACTION_OPEN,
-                buttons=(gtk.STOCK_CANCEL,gtk.RESPONSE_CANCEL,gtk.STOCK_OPEN,gtk.RESPONSE_OK))
-        chooser.set_filename(self.profile)
+        if self.obtain_global_lock():
+            chooser = gtk.FileChooserDialog(title="Please select a profile file to load",
+                    action=gtk.FILE_CHOOSER_ACTION_OPEN,
+                    buttons=(gtk.STOCK_CANCEL,gtk.RESPONSE_CANCEL,gtk.STOCK_OPEN,gtk.RESPONSE_OK))
+            chooser.set_filename(self.profile)
 
-        response = chooser.run()
-        chooser.destroy()    
-        if response == gtk.RESPONSE_OK:
-            self.load_profile(chooser.get_filename())
-        elif response == gtk.RESPONSE_CANCEL:
-            print 'User cancelled loading profile'
+            response = chooser.run()
+            chooser.destroy()    
+            if response == gtk.RESPONSE_OK:
+                self.load_profile(chooser.get_filename())
+            elif response == gtk.RESPONSE_CANCEL:
+                print 'User cancelled loading profile'
     #end def dia_load_profile
 
     def dia_recreate_tables(self, widget, data=None):
         """Dialogue that asks user to confirm that he wants to delete and recreate the tables"""
-        self.obtain_global_lock()
+        if self.obtain_global_lock():
         
-        dia_confirm = gtk.MessageDialog(parent=None, flags=0, type=gtk.MESSAGE_WARNING,
-                buttons=(gtk.BUTTONS_YES_NO), message_format="Confirm deleting and recreating tables")
-        diastring = "Please confirm that you want to (re-)create the tables. If there already are tables in the database "+self.db.database+" on "+self.db.host+" they will be deleted."
-        dia_confirm.format_secondary_text(diastring)#todo: make above string with bold for db, host and deleted
+            dia_confirm = gtk.MessageDialog(parent=None, flags=0, type=gtk.MESSAGE_WARNING,
+                    buttons=(gtk.BUTTONS_YES_NO), message_format="Confirm deleting and recreating tables")
+            diastring = "Please confirm that you want to (re-)create the tables. If there already are tables in the database "+self.db.database+" on "+self.db.host+" they will be deleted."
+            dia_confirm.format_secondary_text(diastring)#todo: make above string with bold for db, host and deleted
 
-        response = dia_confirm.run()
-        dia_confirm.destroy()
-        if response == gtk.RESPONSE_YES:
-            self.db.recreate_tables()
-        elif response == gtk.RESPONSE_NO:
-            print 'User cancelled recreating tables'
+            response = dia_confirm.run()
+            dia_confirm.destroy()
+            if response == gtk.RESPONSE_YES:
+                self.db.recreate_tables()
+            elif response == gtk.RESPONSE_NO:
+                print 'User cancelled recreating tables'
+            self.release_global_lock()
     #end def dia_recreate_tables
 
     def dia_regression_test(self, widget, data=None):
@@ -371,7 +372,14 @@ class fpdb:
     #end def not_implemented
 
     def obtain_global_lock(self):
-        print "todo: implement obtain_global_lock (users: pls ignore this)"
+        print "\nTaking global lock ..."
+        self.fdb_lock = fpdb_db.fpdb_db()
+        self.fdb_lock.connect(self.settings['db-backend'],
+                              self.settings['db-host'],
+                              self.settings['db-databaseName'],
+                              self.settings['db-user'], 
+                              self.settings['db-password'])
+        return fpdb_simple.get_global_lock(self.fdb_lock)
     #end def obtain_global_lock
 
     def quit(self, widget):
@@ -382,7 +390,9 @@ class fpdb:
     #end def quit_cliecked
 
     def release_global_lock(self):
-        print "todo: implement release_global_lock"
+        self.fdb_lock.db.rollback()
+        self.fdb_lock.disconnect()
+        print "Global lock released."
     #end def release_global_lock
 
     def tab_abbreviations(self, widget, data=None):
diff --git a/pyfpdb/fpdb_simple.py b/pyfpdb/fpdb_simple.py
index cecaf09b..c6f79d9d 100644
--- a/pyfpdb/fpdb_simple.py
+++ b/pyfpdb/fpdb_simple.py
@@ -367,6 +367,27 @@ def analyzeDB(fdb):
     fdb.db.commit()
 #end def analyzeDB
 
+def get_global_lock(fdb):
+    if fdb.backend == MYSQL_INNODB:
+        try:
+            fdb.cursor.execute( "lock tables Hands write" )
+        except:
+            print "Error! failed to obtain global lock. Close all programs accessing " \
+                  + "database (including fpdb) and try again (%s)." \
+                  % ( str(sys.exc_value).rstrip('\n'), )
+            return(False)
+    elif fdb.backend == PGSQL:
+        try:
+            fdb.cursor.execute( "lock table Hands in exclusive mode nowait" )
+            #print "... after lock table, status =", fdb.cursor.statusmessage
+        except:
+            print "Error! failed to obtain global lock. Close all programs accessing " \
+                  + "database (including fpdb) and try again (%s)." \
+                  % ( str(sys.exc_value).rstrip('\n'), )
+            return(False)
+    return(True) 
+
+
 class DuplicateError(Exception):
     def __init__(self, value):
         self.value = value