(a) investigate the complaint or cause it to be investigated by an authorised officer, unless he is of the opinion that such complaint is frivolous or vexatious; and (b) as soon as reasonably practicable, notify the complainant in writing of his decision in relation to the complaint and that the complainant may, if he is aggrieved by the Commissioner's decision, appeal to the Tribunal. 12. Enforcement of notice (1) Where the Commissioner is of opinion that a data controller or a data processor has contravened, is contravening or is about to contravene this Act, the Commissioner may serve an enforcement notice on the data controller or the data processor, as the case may be, requiring him to take such steps within such time as may be specified in the notice. (2) Notwithstanding subsection (1), where the Commissioner is of the opinion that a person has committed an offence under this Act, he may investigate the matter or cause it to be investigated by an authorised officer. (3) An enforcement notice shall (a) specify any provision of this Act which has been, is being or is likely to be contravened; (b) specify the measures that shall be taken to remedy or eliminate the matter, as the case may be, which makes it likely that a contravention will arise; (c) specify a time limit which shall not be less than 21 days within which those measures shall be implemented; and (d) state the right of appeal conferred under section 58.