diff --git a/Data/TCache/DefaultPersistence.hs b/Data/TCache/DefaultPersistence.hs
--- a/Data/TCache/DefaultPersistence.hs
+++ b/Data/TCache/DefaultPersistence.hs
@@ -10,7 +10,13 @@
  .The last one defines persistence in files as default, but it can be changed
  to persistence in databases, for examople.
 -}
-module Data.TCache.DefaultPersistence(Indexable(..),Serializable(..),defaultPersist,Persist(..)) where
+module Data.TCache.DefaultPersistence(
+Indexable(..)
+,Serializable(..)
+,setDefaultPersist
+,getDefaultPersist
+,filePersist
+,Persist(..)) where
 
 import System.IO.Unsafe
 import Data.Typeable
@@ -21,8 +27,7 @@
 
 
 
-instance  (Typeable a,  Indexable a, Serializable a ) => IResource a where
-
+instance  (Typeable a,  Indexable a, Serializable a) => IResource a where
   keyResource = key
   writeResource =defWriteResource
   readResourceByKey = defReadResourceByKey
diff --git a/Data/TCache/Defs.hs b/Data/TCache/Defs.hs
--- a/Data/TCache/Defs.hs
+++ b/Data/TCache/Defs.hs
@@ -1,7 +1,7 @@
 {-# LANGUAGE   TypeSynonymInstances, FlexibleInstances, ScopedTypeVariables, DeriveDataTypeable #-}
 
-{- | some internal definitions. To use default persistence, use
-'Data.TCache.DefaultPersistence' instead -}
+{- | some internal definitions. To use default persistence, import
+@Data.TCache.DefaultPersistence@ instead -}
 
 module Data.TCache.Defs  where
 import Data.Typeable
@@ -101,8 +101,8 @@
 class Serializable a  where
   serialize   :: a -> B.ByteString
   deserialize :: B.ByteString -> a
-  setPersist :: a -> Persist         -- ^ `defaultPersist`if not overriden
-  setPersist _= defaultPersist
+  setPersist  :: a -> Maybe Persist              -- ^ `defaultPersist` if Nothing
+  setPersist =  const Nothing
 
 --instance (Show a, Read a)=> Serializable a where
 --  serialize= show
@@ -110,24 +110,32 @@
 
 
 -- | a persist mechanism has to implement these three primitives
--- 'defaultpersist' is the default file persistence
+-- 'filePersist' is the default file persistence
 data Persist = Persist{
        readByKey   ::  (String -> IO(Maybe B.ByteString)) -- ^  read by key. It must be strict
      , write       ::  (String -> B.ByteString -> IO())   -- ^  write. It must be strict
-     , delete      ::  (String -> IO())}       -- ^  delete
+     , delete      ::  (String -> IO())}                  -- ^  delete
 
 -- | Implements default persistence of objects in files with their keys as filenames
-defaultPersist= Persist
+filePersist   = Persist
     {readByKey= defaultReadByKey
-    ,write= defaultWrite
-    ,delete= defaultDelete}
+    ,write    = defaultWrite
+    ,delete   = defaultDelete}
 
-getPersist x= return (setPersist x)
-  `Exception.catch` (\(e:: SomeException) -> error "setPersist must not depend on the type, not the value of the parameter: " )
+defaultPersistIORef = unsafePerformIO $ newIORef  filePersist
 
+-- | Set the default persistence mechanism of all 'serializable' objetcts. By default it is 'filePersist'
+--
+-- this statement must be the first one before any other in TCache
+setDefaultPersist p= writeIORef defaultPersistIORef p
 
+getDefaultPersist =  unsafePerformIO $ readIORef defaultPersistIORef
 
+getPersist x= unsafePerformIO $ case setPersist x of
+     Nothing -> readIORef defaultPersistIORef
+  `Exception.catch` (\(e:: SomeException) -> error "setPersist must depend on the type, not the value of the parameter: " )
 
+
 defaultReadByKey ::   String-> IO (Maybe B.ByteString)
 defaultReadByKey k= iox   -- !> "defaultReadByKey"
      where
@@ -186,18 +194,18 @@
 
 defReadResourceByKey k= iox where
     iox= do
-      let Persist f _ _ = setPersist  x
+      let Persist f _ _ = getPersist  x
       f  file >>=  evaluate . fmap  deserialize
       where
       file= defPath x ++ k
       x= undefined `asTypeOf` (fromJust $ unsafePerformIO iox)
 
 defWriteResource s= do
-      let Persist _ f _ = setPersist  s
+      let Persist _ f _ = getPersist  s
       f (defPath s ++ key s) $ serialize s
 
 defDelResource s= do
-      let Persist _ _ f = setPersist s
+      let Persist _ _ f = getPersist s
       f $ defPath s ++ key s
 
 
diff --git a/Data/TCache/IndexQuery.hs b/Data/TCache/IndexQuery.hs
--- a/Data/TCache/IndexQuery.hs
+++ b/Data/TCache/IndexQuery.hs
@@ -88,7 +88,7 @@
 where
 
 import Data.TCache
-import Data.TCache.Defs
+import Data.TCache.DefaultPersistence
 import Data.List
 import Data.Typeable
 import Control.Concurrent.STM
@@ -109,12 +109,14 @@
       , Typeable a,Ord a)
       => Queriable reg a
 
-instance  Queriable reg a => IResource (Index reg a) where
-  keyResource = key
-  writeResource =defWriteResource
-  readResourceByKey = defReadResourceByKey
-  delResource = defDelResource
+--instance  Queriable reg a => IResource (Index reg a) where
+--  keyResource = key
+--  writeResource =defWriteResource
+--  readResourceByKey = defReadResourceByKey
+--  delResource = defDelResource
 
+
+
 data Index reg a= Index (M.Map a [DBRef reg]) deriving (  Show, Typeable)
 
 instance (IResource reg, Typeable reg,Read reg,Show reg, Show a, Read a, Ord a)
@@ -136,7 +138,7 @@
        where
        [typeofreg, typeofa]= typeRepArgs $! typeOf map
 
-
+   defPath= const ""
 
 getIndex :: (Queriable reg a)
    => ( reg -> a) -> a -> STM(DBRef (Index reg a), Index reg a,[DBRef reg])
diff --git a/Data/TCache/IndexText.hs b/Data/TCache/IndexText.hs
--- a/Data/TCache/IndexText.hs
+++ b/Data/TCache/IndexText.hs
@@ -62,7 +62,7 @@
 , allElemsOf) where
 import Data.TCache
 import Data.TCache.IndexQuery
-import Data.TCache.Defs
+import Data.TCache.DefaultPersistence
 import qualified Data.Text.Lazy as T
 import Data.Typeable
 import qualified Data.Map as M
@@ -102,11 +102,11 @@
 instance  Indexable IndexText  where
    key (IndexText v _ _ _ _)=    "indextext " ++ v
 
-instance IResource IndexText where
-  keyResource = key
-  writeResource =defWriteResource
-  readResourceByKey = defReadResourceByKey
-  delResource = defDelResource
+--instance IResource IndexText where
+--  keyResource = key
+--  writeResource =defWriteResource
+--  readResourceByKey = defReadResourceByKey
+--  delResource = defDelResource
 
 readInitDBRef v x= do
   mv <- readDBRef x
diff --git a/TCache.cabal b/TCache.cabal
--- a/TCache.cabal
+++ b/TCache.cabal
@@ -1,5 +1,5 @@
 name: TCache
-version: 0.10.0.12
+version: 0.10.1.0
 cabal-version: >= 1.6
 build-type: Simple
 license: BSD3
@@ -23,7 +23,7 @@
              .
              In this release:
              .
-             fixed reset of indexes when index, indexText or indexList is used
+             added setDefaultPersist and modified the signature of setPersist in Data.TCache.DefaultPersistence.