diff --git a/ibm_db.c b/ibm_db.c
index 3e4fcda5..61cddbd3 100644
--- a/ibm_db.c
+++ b/ibm_db.c
@@ -1921,6 +1921,8 @@ static PyObject *_python_ibm_db_connect_helper(PyObject *self, PyObject *args, i
     char server[2048];
     int isNewBuffer = 0;
     PyObject *pid = NULL;
+    PyObject *pidStr = NULL;
+    PyObject *threadIdStr = NULL;
     conn_alive = 1;
     if (!PyArg_ParseTuple(args, "OOO|OO", &databaseObj, &uidObj, &passwordObj, &options, &literal_replacementObj))
     {
@@ -1977,9 +1979,24 @@ static PyObject *_python_ibm_db_connect_helper(PyObject *self, PyObject *args, i
             }
             snprintf(messageStr, sizeof(messageStr), "Obtain process id: %p", pid);
             LogMsg(INFO, messageStr);
-            hKey = PyUnicode_Concat(hKey, PyUnicode_FromFormat("%ld", PyLong_AsLong(pid)));
+            pidStr = PyUnicode_FromFormat("%ld", PyLong_AsLong(pid));
+            if (pidStr == NULL)
+            {
+                Py_DECREF(pid);
+                return NULL;
+            }
+            hKey = PyUnicode_Concat(hKey, pidStr);
+            Py_DECREF(pidStr);
             Py_DECREF(pid);
 
+            threadIdStr = PyUnicode_FromFormat("%ld", (long)PyThread_get_thread_ident());
+            if (threadIdStr == NULL)
+            {
+                return NULL;
+            }
+            hKey = PyUnicode_Concat(hKey, threadIdStr);
+            Py_DECREF(threadIdStr);
+
             entry = PyDict_GetItem(persistent_list, hKey);
 
             if (entry != NULL)
@@ -4274,7 +4291,8 @@ static PyObject *ibm_db_bind_param(PyObject *self, PyObject *args)
  *    Specifies an active DB2 client connection.
  *
  * ===Return Values
- * Returns TRUE on success or FALSE on failure.
+ * Returns TRUE on success. If the connection is already closed, returns TRUE.
+ * On failure, an exception is raised and NULL is returned.
  */
 static PyObject *ibm_db_close(PyObject *self, PyObject *args)
 {
@@ -4314,9 +4332,10 @@ static PyObject *ibm_db_close(PyObject *self, PyObject *args)
 
         if (!conn_res->handle_active)
         {
-            LogMsg(EXCEPTION, "Connection is not active");
-            PyErr_SetString(PyExc_Exception, "Connection is not active");
-            return NULL;
+            LogMsg(INFO, "Connection already closed; no action required");
+            Py_INCREF(Py_True);
+            LogMsg(INFO, "exit close()");
+            return Py_True;
         }
 
         if (conn_res->handle_active && !conn_res->flag_pconnect)
diff --git a/ibm_db_dbi.py b/ibm_db_dbi.py
index ece68a6d..ee7e43f6 100644
--- a/ibm_db_dbi.py
+++ b/ibm_db_dbi.py
@@ -923,20 +923,22 @@ def close(self):
         """This method closes the Database connection associated with
         the Connection object.  It takes no arguments.
 
+        If the connection is already closed, this method is a no-op and
+        returns True.
+
         """
         LogMsg(INFO, "entry close()")
-        self.rollback()
-        try:
-            if self.conn_handler is None:
-                LogMsg(ERROR, "Connection cannot be closed; connection is no longer active.")
-                raise ProgrammingError("Connection cannot be closed; "
-                                       "connection is no longer active.")
-            else:
+        if self.conn_handler is None:
+            return_value = True
+            LogMsg(INFO, "Connection already closed; no action required.")
+        else:
+            self.rollback()
+            try:
                 return_value = ibm_db.close(self.conn_handler)
                 LogMsg(INFO, "Connection closed.")
-        except Exception as inst:
-            LogMsg(EXCEPTION, f"An exception occurred while closing connection: {inst}")
-            raise _get_exception(inst)
+            except Exception as inst:
+                LogMsg(EXCEPTION, f"An exception occurred while closing connection: {inst}")
+                raise _get_exception(inst)
         self.conn_handler = None
         for index in range(len(self._cursor_list)):
             if (self._cursor_list[index]() != None):
diff --git a/ibm_db_tests/test_072_CloseTwice_DBI.py b/ibm_db_tests/test_072_CloseTwice_DBI.py
new file mode 100644
index 00000000..0f8bc254
--- /dev/null
+++ b/ibm_db_tests/test_072_CloseTwice_DBI.py
@@ -0,0 +1,42 @@
+#
+#  Licensed Materials - Property of IBM
+#
+#  (c) Copyright IBM Corp. 2026
+#
+
+from __future__ import print_function
+import sys
+import unittest
+import ibm_db_dbi
+import config
+from testfunctions import IbmDbTestFunctions
+
+
+class IbmDbTestCase(unittest.TestCase):
+
+    def test_072_CloseTwice_DBI(self):
+        obj = IbmDbTestFunctions()
+        obj.assert_expect(self.run_test_072)
+
+    def run_test_072(self):
+        conn = ibm_db_dbi.connect(config.database, config.user, config.password)
+
+        rc1 = conn.close()
+        rc2 = conn.close()
+
+        print(rc1)
+        print(rc2)
+
+#__END__
+#__LUW_EXPECTED__
+#True
+#True
+#__ZOS_EXPECTED__
+#True
+#True
+#__SYSTEMI_EXPECTED__
+#True
+#True
+#__IDS_EXPECTED__
+#True
+#True
diff --git a/ibm_db_tests/test_6793_PconnectThreadIsolation.py b/ibm_db_tests/test_6793_PconnectThreadIsolation.py
new file mode 100644
index 00000000..ec1528e7
--- /dev/null
+++ b/ibm_db_tests/test_6793_PconnectThreadIsolation.py
@@ -0,0 +1,90 @@
+#
+#  Licensed Materials - Property of IBM
+#
+#  (c) Copyright IBM Corp. 2007-2008
+#
+
+from __future__ import print_function
+import sys
+import threading
+import unittest
+import ibm_db
+import config
+from testfunctions import IbmDbTestFunctions
+
+
+class IbmDbTestCase(unittest.TestCase):
+
+    def test_6793_PconnectThreadIsolation(self):
+        obj = IbmDbTestFunctions()
+        obj.assert_expect(self.run_test_6793)
+
+    def run_test_6793(self):
+        start_event = threading.Event()
+        lock = threading.Lock()
+        results = []
+        errors = []
+
+        def worker():
+            try:
+                start_event.wait()
+
+                if sys.platform == 'zos':
+                    conn = ibm_db.pconnect(config.database, '', '')
+                else:
+                    conn = ibm_db.pconnect(config.database, config.user, config.password)
+
+                if not conn:
+                    with lock:
+                        errors.append("connect_failed")
+                    return
+
+                is_active = ibm_db.active(conn)
+                conn_id = id(conn)
+                ibm_db.close(conn)
+
+                with lock:
+                    results.append((conn_id, is_active))
+            except Exception:
+                with lock:
+                    errors.append("worker_exception")
+
+        threads = [threading.Thread(target=worker) for _ in range(2)]
+
+        for t in threads:
+            t.start()
+
+        start_event.set()
+
+        for t in threads:
+            t.join()
+
+        if errors:
+            print("errors:", len(errors))
+            return
+
+        unique_conn_handles = len(set([conn_id for conn_id, _ in results]))
+        active_count = sum(1 for _, is_active in results if is_active)
+
+        print("workers:", len(results))
+        print("active_count:", active_count)
+        print("unique_conn_handles:", unique_conn_handles)
+
+
+#__END__
+#__LUW_EXPECTED__
+#workers: 2
+#active_count: 2
+#unique_conn_handles: 2
+#__ZOS_EXPECTED__
+#workers: 2
+#active_count: 2
+#unique_conn_handles: 2
+#__SYSTEMI_EXPECTED__
+#workers: 2
+#active_count: 2
+#unique_conn_handles: 2
+#__IDS_EXPECTED__
+#workers: 2
+#active_count: 2
+#unique_conn_handles: 2