This excerpt taken from the PCG 10-K filed Feb 18, 2005.
17.1. Records Relevant to Operation of ISO Controlled Grid.
The ISO shall keep such records as may be necessary for the efficient operation of the ISO Controlled Grid and shall make appropriate records available to a Participating TO, upon request. The ISO shall maintain for not less than five (5) years: (1) a record of its operating orders and (2) a record of the contents of, and changes to, the ISO Register.