diff --git a/python_tests/test_storage_stats.py b/python_tests/test_storage_stats.py
index 3c0d4cc2..447af92b 100644
--- a/python_tests/test_storage_stats.py
+++ b/python_tests/test_storage_stats.py
@@ -69,12 +69,12 @@ def test_io_operation_stability(db0_large_lang_cache_no_autocommit):
             number = (i*iterations + j)%indexes_count
             index_container = indexes.indexes[number]
             now = datetime.now()
-            new_value = Value(index_number=number, date=now, value=list_value)
+            new_value = Value(index_number=number, date=now, value=BYTES)
             index_container.index.add(now, new_value)
         
         # calculate objects per second
         stop = datetime.now()
-        seconds = (stop - start).miliseconds / 1000.0
+        seconds = (stop - start).seconds
         print(f" Objects per second: {iterations / seconds}")
 
         # commit changes
diff --git a/src/dbzero/core/storage/CFile.cpp b/src/dbzero/core/storage/CFile.cpp
index e6ce4649..1969f53d 100644
--- a/src/dbzero/core/storage/CFile.cpp
+++ b/src/dbzero/core/storage/CFile.cpp
@@ -215,8 +215,13 @@ namespace db0
             flush(lock);
         }
         if (address != m_file_pos) {
+            // static counter of random read operations
+
             setFilePos(address, lock);
             ++m_rand_read_ops;
+            if (m_rand_read_ops > 3) {
+                throw std::runtime_error("Too many random read operations");
+            }
         }
         assert(m_file_pos == (std::uint64_t)ftell(m_file));
         if (fread(buffer, size, 1, m_file) != 1) {