diff --git a/core/includes/module.inc b/core/includes/module.inc
index d674866..17f087c 100644
--- a/core/includes/module.inc
+++ b/core/includes/module.inc
@@ -8,7 +8,7 @@
 use Drupal\Component\Graph\Graph;
 
 /**
- * Loads all the modules that have been enabled in the system table.
+ * Loads all enabled modules.
  *
  * @param bool $bootstrap
  *   Whether to load only the reduced set of modules loaded in "bootstrap mode"
@@ -387,7 +387,7 @@ function module_load_include($type, $module, $name = NULL) {
 }
 
 /**
- * Loads an include file for each module enabled in the {system} table.
+ * Loads an include file for each enabled module.
  */
 function module_load_all_includes($type, $name = NULL) {
   $modules = module_list();
diff --git a/core/includes/schema.inc b/core/includes/schema.inc
index bff33d3..f46739c 100644
--- a/core/includes/schema.inc
+++ b/core/includes/schema.inc
@@ -166,7 +166,7 @@ function drupal_get_schema_versions($module) {
  * @param string $module
  *   A module name.
  * @param bool $reset
- *   Set to TRUE after modifying the system table.
+ *   Set to TRUE after installing or uninstalling an extension.
  * @param bool $array
  *   Set to TRUE if you want to get information about all modules in the
  *   system.
diff --git a/core/includes/update.inc b/core/includes/update.inc
index 99dd714..1dc1548 100644
--- a/core/includes/update.inc
+++ b/core/includes/update.inc
@@ -18,7 +18,7 @@
  * Upgrades from Drupal 7 to Drupal 8 require that Drupal 7 be running
  * the most recent version, or the upgrade could fail. We can't easily
  * check the Drupal 7 version once the update process has begun, so instead
- * we check the schema version of system.module in the system table.
+ * we check the schema version of system.module.
  */
 const REQUIRED_D7_SCHEMA_VERSION = '7069';
 
@@ -217,6 +217,8 @@ function update_prepare_d8_bootstrap() {
       // requirements check.
       require_once DRUPAL_ROOT . '/core/modules/system/system.module';
 
+      // Retrieve all installed extensions from the {system} table.
+      // Uninstalled extensions are ignored and not converted.
       $result = db_query('SELECT name, status, weight, schema_version, type FROM {system} WHERE type = :theme OR (type = :module AND schema_version <> :schema_uninstalled)', array(
         ':theme' => 'theme',
         ':module' => 'module',
@@ -224,7 +226,8 @@ function update_prepare_d8_bootstrap() {
       ));
       $module_data = _system_rebuild_module_data();
 
-      // Loop through each extension from the system table.
+      // Migrate each extension into configuration, varying by the extension's
+      // status, and record its schema version.
       foreach ($result as $record) {
         if ($record->type == 'module') {
           if ($record->status && isset($module_data[$record->name])) {
@@ -233,7 +236,6 @@ function update_prepare_d8_bootstrap() {
           else {
             $disabled_modules->set($record->name, $record->weight);
           }
-          $schema_store->set($record->name, $record->schema_version);
         }
         elseif ($record->type == 'theme') {
           if ($record->status) {
@@ -243,6 +245,7 @@ function update_prepare_d8_bootstrap() {
             $disabled_themes->set($record->name, 0);
           }
         }
+        $schema_store->set($record->name, $record->schema_version);
       }
       $module_config->set('enabled', module_config_sort($module_config->get('enabled')))->save();
       $disabled_modules->save();
diff --git a/core/lib/Drupal/Core/Updater/Theme.php b/core/lib/Drupal/Core/Updater/Theme.php
index 16bb515..4bd716a 100644
--- a/core/lib/Drupal/Core/Updater/Theme.php
+++ b/core/lib/Drupal/Core/Updater/Theme.php
@@ -72,7 +72,7 @@ public static function canUpdate($project_name) {
    * Overrides Drupal\Core\Updater\Updater::postInstall().
    */
   public function postInstall() {
-    // Update the system table.
+    // Update the theme info.
     clearstatcache();
     system_rebuild_theme_data();
   }
diff --git a/core/modules/locale/lib/Drupal/locale/Tests/LocaleCompareTest.php b/core/modules/locale/lib/Drupal/locale/Tests/LocaleCompareTest.php
index 112fee8..1d2ec67 100644
--- a/core/modules/locale/lib/Drupal/locale/Tests/LocaleCompareTest.php
+++ b/core/modules/locale/lib/Drupal/locale/Tests/LocaleCompareTest.php
@@ -47,11 +47,12 @@ function testLocaleCompare() {
     // modules not hidden. locale_test_system_info_alter() modifies the project
     // info of the locale_test and locale_test_disabled modules.
     variable_set('locale_translation_test_system_info_alter', TRUE);
-    // Reset system lists to reflect changes.
+
+    // Reset static system list caches to reflect info changes.
+    drupal_static_reset('locale_translation_project_list');
     system_list_reset();
 
     // Check if interface translation data is collected from hook_info.
-    drupal_static_reset('locale_translation_project_list');
     $projects = locale_translation_project_list();
     $this->assertEqual($projects['locale_test']['info']['interface translation server pattern'], 'core/modules/locale/test/modules/locale_test/%project-%version.%language.po', 'Interface translation parameter found in project info.');
     $this->assertEqual($projects['locale_test']['name'] , 'locale_test', format_string('%key found in project info.', array('%key' => 'interface translation project')));
diff --git a/core/modules/system/lib/Drupal/system/Tests/Database/RangeQueryTest.php b/core/modules/system/lib/Drupal/system/Tests/Database/RangeQueryTest.php
index f85750b..60db2b3 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Database/RangeQueryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Database/RangeQueryTest.php
@@ -7,12 +7,10 @@
 
 namespace Drupal\system\Tests\Database;
 
-use Drupal\simpletest\WebTestBase;
-
 /**
  * Range query tests.
  */
-class RangeQueryTest extends WebTestBase {
+class RangeQueryTest extends DatabaseTestBase {
 
   /**
    * Modules to enable.
@@ -34,12 +32,12 @@ public static function getInfo() {
    */
   function testRangeQuery() {
     // Test if return correct number of rows.
-    $range_rows = db_query_range("SELECT name FROM {variable} ORDER BY name", 2, 3)->fetchAll();
+    $range_rows = db_query_range("SELECT name FROM {test} ORDER BY name", 1, 3)->fetchAll();
     $this->assertEqual(count($range_rows), 3, 'Range query work and return correct number of rows.');
 
     // Test if return target data.
-    $raw_rows = db_query('SELECT name FROM {variable} ORDER BY name')->fetchAll();
-    $raw_rows = array_slice($raw_rows, 2, 3);
-    $this->assertEqual($range_rows, $raw_rows, 'Range query work and return target data.');
+    $raw_rows = db_query('SELECT name FROM {test} ORDER BY name')->fetchAll();
+    $raw_rows = array_slice($raw_rows, 1, 3);
+    $this->assertEqual($range_rows, $raw_rows);
   }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Database/TemporaryQueryTest.php b/core/modules/system/lib/Drupal/system/Tests/Database/TemporaryQueryTest.php
index 110f5a8..7c2d0d0 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Database/TemporaryQueryTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Database/TemporaryQueryTest.php
@@ -7,12 +7,10 @@
 
 namespace Drupal\system\Tests\Database;
 
-use Drupal\simpletest\WebTestBase;
-
 /**
  * Temporary query tests.
  */
-class TemporaryQueryTest extends WebTestBase {
+class TemporaryQueryTest extends DatabaseTestBase {
 
   /**
    * Modules to enable.
@@ -43,7 +41,7 @@ function testTemporaryQuery() {
     $this->drupalGet('database_test/db_query_temporary');
     $data = json_decode($this->drupalGetContent());
     if ($data) {
-      $this->assertEqual($this->countTableRows("filter"), $data->row_count, 'The temporary table contains the correct amount of rows.');
+      $this->assertEqual($this->countTableRows('test'), $data->row_count, 'The temporary table contains the correct amount of rows.');
       $this->assertFalse(db_table_exists($data->table_name), 'The temporary table is, indeed, temporary.');
     }
     else {
@@ -51,10 +49,10 @@ function testTemporaryQuery() {
     }
 
     // Now try to run two db_query_temporary() in the same request.
-    $table_name_system = db_query_temporary('SELECT name FROM {variable}', array());
-    $table_name_users = db_query_temporary('SELECT uid FROM {users}', array());
+    $table_name_test = db_query_temporary('SELECT name FROM {test}', array());
+    $table_name_task = db_query_temporary('SELECT pid FROM {test_task}', array());
 
-    $this->assertEqual($this->countTableRows($table_name_system), $this->countTableRows("variable"), 'A temporary table was created successfully in this request.');
-    $this->assertEqual($this->countTableRows($table_name_users), $this->countTableRows("users"), 'A second temporary table was created successfully in this request.');
+    $this->assertEqual($this->countTableRows($table_name_test), $this->countTableRows('test'), 'A temporary table was created successfully in this request.');
+    $this->assertEqual($this->countTableRows($table_name_task), $this->countTableRows('test_task'), 'A second temporary table was created successfully in this request.');
   }
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/System/InfoAlterTest.php b/core/modules/system/lib/Drupal/system/Tests/System/InfoAlterTest.php
index 603af18..8d004ab 100644
--- a/core/modules/system/lib/Drupal/system/Tests/System/InfoAlterTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/System/InfoAlterTest.php
@@ -22,20 +22,21 @@ public static function getInfo() {
   }
 
   /**
-   * Tests that {system}.info is rebuilt after a module that implements
+   * Tests that theme .info data is rebuild after enabling a module.
+   *
+   * Tests that info data is rebuilt after a module that implements
    * hook_system_info_alter() is enabled. Also tests if core *_list() functions
    * return freshly altered info.
    */
   function testSystemInfoAlter() {
-    // Enable seven and the test module. Flush all caches, which we assert is
-    // the only thing necessary to use the rebuilt {system}.info.
+    // Enable seven and the test module.
     theme_enable(array('seven'));
     module_enable(array('module_test'), FALSE);
-    $this->resetAll();
     $this->assertTrue(module_exists('module_test'), t('Test module is enabled.'));
 
+    // Verify that the rebuilt and altered theme info is returned.
     $info = system_get_info('theme', 'seven');
-    $this->assertTrue(isset($info['regions']['test_region']), t('Altered theme info was added to {system}.info.'));
+    $this->assertTrue(isset($info['regions']['test_region']), t('Altered theme info was returned by system_get_info().'));
     $seven_regions = system_region_list('seven');
     $this->assertTrue(isset($seven_regions['test_region']), t('Altered theme info was returned by system_region_list().'));
     $system_list_themes = system_list('theme');
@@ -44,13 +45,12 @@ function testSystemInfoAlter() {
     $list_themes = list_themes();
     $this->assertTrue(isset($list_themes['seven']->info['regions']['test_region']), t('Altered theme info was returned by list_themes().'));
 
-    // Disable the module and verify that {system}.info is rebuilt without it.
+    // Disable the module and verify that rebuilt .info does not contain it.
     module_disable(array('module_test'), FALSE);
-    $this->resetAll();
     $this->assertFalse(module_exists('module_test'), t('Test module is disabled.'));
 
     $info = system_get_info('theme', 'seven');
-    $this->assertFalse(isset($info['regions']['test_region']), t('Altered theme info was removed from {system}.info.'));
+    $this->assertFalse(isset($info['regions']['test_region']), t('Altered theme info was not returned by system_get_info().'));
     $seven_regions = system_region_list('seven');
     $this->assertFalse(isset($seven_regions['test_region']), t('Altered theme info was not returned by system_region_list().'));
     $system_list_themes = system_list('theme');
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index dd263cd..0f6d668 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -2167,10 +2167,7 @@ function hook_cache_flush() {
  * @see drupal_flush_all_caches()
  */
 function hook_rebuild() {
-  // Rehash blocks for active themes. We don't use list_themes() here,
-  // because if MAINTENANCE_MODE is defined it skips reading the database,
-  // and we can't tell which themes are active.
-  $themes = db_query("SELECT name FROM {system} WHERE type = 'theme' AND status = 1");
+  $themes = list_themes();
   foreach ($themes as $theme) {
     _block_rehash($theme->name);
   }
@@ -2983,8 +2980,8 @@ function hook_update_last_removed() {
  * - variables that the module has set using variable_set() or system_settings_form()
  * - modifications to existing tables
  *
- * The module should not remove its entry from the {system} table. Database
- * tables defined by hook_schema() will be removed automatically.
+ * The module should not remove its entry from the module configuration.
+ * Database tables defined by hook_schema() will be removed automatically.
  *
  * The uninstall hook must be implemented in the module's .install file. It
  * will fire when the module gets uninstalled but before the module's database
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 7b34f3f..cc8fc9c 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -2655,8 +2655,8 @@ function system_check_directory($form_element) {
 /**
  * Returns an array of information about enabled modules or themes.
  *
- * This function returns the information from the {system} table corresponding
- * to the cached contents of the .info file for each active module or theme.
+ * This function returns the contents of the .info file for each enabled module
+ * or theme.
  *
  * @param $type
  *   Either 'module' or 'theme'.
@@ -2841,7 +2841,7 @@ function system_rebuild_module_data() {
 }
 
 /**
- * Refresh bootstrap column in the system table.
+ * Refreshes the list of bootstrap modules.
  *
  * This is called internally by module_enable/disable() to flag modules that
  * implement hooks used during bootstrap, such as hook_boot(). These modules
diff --git a/core/modules/system/tests/modules/database_test/database_test.module b/core/modules/system/tests/modules/database_test/database_test.module
index 93135c9..339f1f9 100644
--- a/core/modules/system/tests/modules/database_test/database_test.module
+++ b/core/modules/system/tests/modules/database_test/database_test.module
@@ -84,7 +84,7 @@ function database_test_menu() {
  * table should automatically dropped.
  */
 function database_test_db_query_temporary() {
-  $table_name = db_query_temporary('SELECT status FROM {filter}', array());
+  $table_name = db_query_temporary('SELECT age FROM {test}', array());
   return new JsonResponse(array(
     'table_name' => $table_name,
     'row_count' => db_select($table_name)->countQuery()->execute()->fetchField(),
diff --git a/core/modules/update/update.authorize.inc b/core/modules/update/update.authorize.inc
index d22f235..4557453 100644
--- a/core/modules/update/update.authorize.inc
+++ b/core/modules/update/update.authorize.inc
@@ -66,7 +66,8 @@ function update_authorize_run_update($filetransfer, $projects) {
  *   The FileTransfer object created by authorize.php for use during this
  *   operation.
  * @param string $project
- *   The canonical project short name (e.g., {system}.name).
+ *   The canonical project short name; i.e., the name of the module, theme, or
+ *   profile.
  * @param string $updater_name
  *   The name of the Drupal\Core\Updater\Updater class to use for installing
  *   this project.