diff --git a/DataFormats/Common/interface/Ptr.h b/DataFormats/Common/interface/Ptr.h
index 613bf0be4d5b4..09b819220b229 100644
--- a/DataFormats/Common/interface/Ptr.h
+++ b/DataFormats/Common/interface/Ptr.h
@@ -149,6 +149,8 @@ namespace edm {
 
     /// Checks if collection is in memory or available
     /// in the event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
     bool isAvailable() const;
 
     /// Checks if this Ptr is transient (i.e. not persistable).
diff --git a/DataFormats/Common/interface/Ref.h b/DataFormats/Common/interface/Ref.h
index c5fbfcc4a10eb..396fcea17a66b 100644
--- a/DataFormats/Common/interface/Ref.h
+++ b/DataFormats/Common/interface/Ref.h
@@ -257,6 +257,8 @@ namespace edm {
 
     /// Checks if collection is in memory or available
     /// in the Event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
     bool isAvailable() const;
 
     /// Checks if this ref is transient (i.e. not persistable).
@@ -404,6 +406,8 @@ namespace edm {
 
     /// Checks if collection is in memory or available
     /// in the Event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
     bool isAvailable() const;
 
     /// Checks if this ref is transient (i.e. not persistable).
diff --git a/DataFormats/Common/interface/RefCoreWithIndex.h b/DataFormats/Common/interface/RefCoreWithIndex.h
index 9098d28db108b..595cfeaba011d 100644
--- a/DataFormats/Common/interface/RefCoreWithIndex.h
+++ b/DataFormats/Common/interface/RefCoreWithIndex.h
@@ -88,7 +88,8 @@ namespace edm {
 
     // Checks if collection is in memory or available
     // in the Event. No type checking is done.
-
+    // This function is potentially costly as it might cause a disk
+    // read (note that it does not cause the data to be cached locally)
     bool isAvailable() const { return toRefCore().isAvailable(); }
 
     //Convert to an equivalent RefCore. Needed for Ref specialization.
diff --git a/DataFormats/Common/interface/RefProd.h b/DataFormats/Common/interface/RefProd.h
index b5f40fd293bcf..c17a5f2d821ee 100644
--- a/DataFormats/Common/interface/RefProd.h
+++ b/DataFormats/Common/interface/RefProd.h
@@ -134,6 +134,8 @@ namespace edm {
 
     /// Checks if collection is in memory or available
     /// in the Event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
     bool isAvailable() const { return product_.isAvailable(); }
 
     /// Checks if this RefProd is transient (i.e. not persistable).
diff --git a/DataFormats/Common/interface/RefToBase.h b/DataFormats/Common/interface/RefToBase.h
index d46226f0de93c..d12434a65b4a7 100644
--- a/DataFormats/Common/interface/RefToBase.h
+++ b/DataFormats/Common/interface/RefToBase.h
@@ -116,6 +116,8 @@ namespace edm {
 
     /// Checks if collection is in memory or available
     /// in the Event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
     bool isAvailable() const { return holder_ ? holder_->isAvailable() : false; }
 
     bool isTransient() const { return holder_ ? holder_->isTransient() : false; }
diff --git a/DataFormats/Common/interface/RefToBaseProd.h b/DataFormats/Common/interface/RefToBaseProd.h
index bbac746d107fa..b046ea271419f 100644
--- a/DataFormats/Common/interface/RefToBaseProd.h
+++ b/DataFormats/Common/interface/RefToBaseProd.h
@@ -66,6 +66,12 @@ namespace edm {
     /// Checks for non-null
     bool isNonnull() const { return product_.isNonnull(); }
 
+    /// Checks if collection is in memory or available
+    /// in the Event. No type checking is done.
+    /// This function is potentially costly as it might cause a disk
+    /// read (note that it does not cause the data to be cached locally)
+    bool isAvailable() const { return product_.isAvailable(); }
+
     /// Checks for null
     bool operator!() const { return isNull(); }
 
diff --git a/DataFormats/Common/test/reftobaseprod_t.cppunit.cc b/DataFormats/Common/test/reftobaseprod_t.cppunit.cc
index 02ab42145d08b..45564b64125f5 100644
--- a/DataFormats/Common/test/reftobaseprod_t.cppunit.cc
+++ b/DataFormats/Common/test/reftobaseprod_t.cppunit.cc
@@ -93,11 +93,13 @@ void testRefToBaseProd::constructTest() {
   CPPUNIT_ASSERT(!nulled);
   CPPUNIT_ASSERT(nulled.isNull());
   CPPUNIT_ASSERT(!nulled.isNonnull());
+  CPPUNIT_ASSERT(!nulled.isAvailable());
 
   RefToBaseProd<Dummy> nulledP;
   CPPUNIT_ASSERT(!nulledP);
   CPPUNIT_ASSERT(nulledP.isNull());
   CPPUNIT_ASSERT(!nulledP.isNonnull());
+  CPPUNIT_ASSERT(!nulledP.isAvailable());
 
   ProductID const pid(1, 1);
 
@@ -110,6 +112,9 @@ void testRefToBaseProd::constructTest() {
     OrphanHandle<DummyCollection> handle(&dummyContainer, pid);
     RefToBaseProd<Dummy> dummyPtr(handle);
 
+    CPPUNIT_ASSERT(!dummyPtr.isNull());
+    CPPUNIT_ASSERT(dummyPtr.isNonnull());
+    CPPUNIT_ASSERT(dummyPtr.isAvailable());
     CPPUNIT_ASSERT(dummyPtr.id() == pid);
     compareTo(dummyPtr, dummyContainer);
   }
@@ -218,9 +223,15 @@ void testRefToBaseProd::getTest() {
 
     RefCore core(pid, nullptr, &tester, false);
     RefToBaseProd<IntValue>& prod = reinterpret_cast<RefToBaseProd<IntValue>&>(core);
+    CPPUNIT_ASSERT(!prod.isNull());
+    CPPUNIT_ASSERT(prod.isNonnull());
+    CPPUNIT_ASSERT(prod.isAvailable());
 
     //previously making a copy before reading back would cause seg fault
     RefToBaseProd<IntValue> prodCopy(prod);
+    CPPUNIT_ASSERT(!prodCopy.isNull());
+    CPPUNIT_ASSERT(prodCopy.isNonnull());
+    CPPUNIT_ASSERT(prodCopy.isAvailable());
 
     CPPUNIT_ASSERT(!prod.hasCache());