It is not possible to default list out all possible records due to the potential of a performance issue when returning for such queries. However, in Service Desk Options Manager (accessible by logging into the SDM Web interface as a user with Admin privileges), the following settings dictate the number of records returned by REST Web Services:
Specifies the maximum number of rows that a REST Web Service query returns.
Specifies the default number of rows that a REST Web Service query returns per page.
Valid Range: 1-500
We have experimentally tested providing a very large integer value which would exceed the valid range for option "rest_webservice_list_page_length" with some success. However, such testing was not very rigorous and we would suggest to abide by the recommended range value that is given.