(64) The controller should use all reasonable measures to verify the identity of a data subject who requests access, in particular in the context of online services and online identifiers.
A controller should not retain personal data for the sole purpose of being able to react to potential requests.
The latest consolidated version of the Regulation with corrections by Corrigendum, OJ L 127, 23.5.2018, p. 2 ((EU) 2016/679). Source: EUR-lex.