9 files declare their use of Schema

BatchStorage.php in core/lib/Drupal/Core/Batch/BatchStorage.php
database.api.php in core/lib/Drupal/Core/Database/database.api.php
Hooks related to the Database system and the Schema API.
KernelTestBase.php in core/tests/Drupal/KernelTests/KernelTestBase.php
locale.install in core/modules/locale/locale.install
Install, update, and uninstall functions for the Locale module.
ModuleInstaller.php in core/lib/Drupal/Core/Extension/ModuleInstaller.php
Schema.php in core/lib/Drupal/Core/Database/Schema.php
SchemaDefinitionConversionTest.php in core/tests/Drupal/Tests/Core/Database/SchemaDefinitionConversionTest.php
SchemaDefinitionTest.php in core/tests/Drupal/Tests/Core/Database/SchemaDefinitionTest.php
SchemaInspector.php in core/tests/Drupal/TestTools/Extension/SchemaInspector.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.