4 calls to db_next_id()

actions_save in includes/actions.inc
Saves an action and its user-supplied parameter values to the database.
batch_process in includes/form.inc
Processes the batch.
DatabaseNextIdCase::testDbNextId in modules/simpletest/tests/database_test.test
Test that the sequences API work.
user_save in modules/user/user.module
Save changes to a user account or add a new user.

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