1. A computer program product comprising a non-transitory computer-readable storage medium having code stored thereon, the code, when executed by a processor, causing the processor to implement a data copy method, the method comprising: performing a first copy operation to generate first copy data in a snapshot format, without generating a corresponding index to the first copy data for browsing the first copy data in the snapshot format; performing a second copy operation on the first copy data in the snapshot format to generate second copy data in a second copy format, wherein the second copy data in the second copy format is data in a nested format that includes the first copy data in the snapshot format; and generating an index table comprising entries for one or more data items from the first copy data stored in the second copy data in the second copy format, wherein each entry includes— data item identification information that identifies a data item associated with the entry; first access information for the data item to allow access to the data item in the second copy data, wherein the first access information comprises an archive file identification from a set of pre-determined archive file identification values indicating that a corresponding archive file is storing data in the snapshot format, second access information to allow access to the data item in the first copy data, thereby allowing direct access to the data item based on information from the index table; and format information for the data item that identifies a level of format nesting for the data item within the first copy data and the second copy data.