diff --git a/django/db/backends/creation.py b/django/db/backends/creation.py
index 2db0acca7c..0cd055866a 100644
--- a/django/db/backends/creation.py
+++ b/django/db/backends/creation.py
@@ -353,7 +353,7 @@ class BaseDatabaseCreation(object):
     def destroy_test_db(self, old_database_name, verbosity=1):
         """
         Destroy a test database, prompting the user for confirmation if the
-        database already exists. Returns the name of the test database created.
+        database already exists.
         """
         self.connection.close()
         test_database_name = self.connection.settings_dict['NAME']
@@ -367,7 +367,7 @@ class BaseDatabaseCreation(object):
         # Temporarily use a new connection and a copy of the settings dict.
         # This prevents the production database from being exposed to potential
         # child threads while (or after) the test database is destroyed.
-        # Refs #10868.
+        # Refs #10868 and #17786.
         settings_dict = self.connection.settings_dict.copy()
         settings_dict['NAME'] = old_database_name
         backend = load_backend(settings_dict['ENGINE'])
diff --git a/django/db/backends/oracle/creation.py b/django/db/backends/oracle/creation.py
index c6b04da57f..9e6133fc64 100644
--- a/django/db/backends/oracle/creation.py
+++ b/django/db/backends/oracle/creation.py
@@ -40,11 +40,6 @@ class DatabaseCreation(BaseDatabaseCreation):
         'URLField':                     'VARCHAR2(%(max_length)s)',
     }
 
-    # This dictionary stores the original values of user and passwd, which are
-    # changed during the tests. It's stored at the class level because the
-    # test database is created and destroyed by different connections (#17786).
-    remember = {}
-
     def __init__(self, connection):
         super(DatabaseCreation, self).__init__(connection)
 
@@ -63,9 +58,6 @@ class DatabaseCreation(BaseDatabaseCreation):
             'tblspace_temp': TEST_TBLSPACE_TMP,
         }
 
-        self.remember['user'] = self.connection.settings_dict['USER']
-        self.remember['passwd'] = self.connection.settings_dict['PASSWORD']
-
         cursor = self.connection.cursor()
         if self._test_database_create():
             try:
@@ -111,8 +103,10 @@ class DatabaseCreation(BaseDatabaseCreation):
                     print "Tests cancelled."
                     sys.exit(1)
 
-        self.connection.settings_dict['TEST_USER'] = self.connection.settings_dict["USER"] = TEST_USER
-        self.connection.settings_dict["PASSWORD"] = TEST_PASSWD
+        self.connection.settings_dict['SAVED_USER'] = self.connection.settings_dict['USER']
+        self.connection.settings_dict['SAVED_PASSWORD'] = self.connection.settings_dict['PASSWORD']
+        self.connection.settings_dict['TEST_USER'] = self.connection.settings_dict['USER'] = TEST_USER
+        self.connection.settings_dict['PASSWORD'] = TEST_PASSWD
 
         return self.connection.settings_dict['NAME']
 
@@ -127,8 +121,8 @@ class DatabaseCreation(BaseDatabaseCreation):
         TEST_TBLSPACE = self._test_database_tblspace()
         TEST_TBLSPACE_TMP = self._test_database_tblspace_tmp()
 
-        self.connection.settings_dict["USER"] = self.remember['user']
-        self.connection.settings_dict["PASSWORD"] = self.remember['passwd']
+        self.connection.settings_dict['USER'] = self.connection.settings_dict['SAVED_USER']
+        self.connection.settings_dict['PASSWORD'] = self.connection.settings_dict['SAVED_PASSWORD']
 
         parameters = {
             'dbname': TEST_NAME,