...
The above diagram (Source) depicts the optimizations carried out to improve the performance of the REST service API while handling huge volume of data.
The parameters required by the API call is well defined on the swagger documentation.
NOTE: Generating a full dump (fetchType = Full) is a time and resource consuming job and typically is run only the very first time to get all data from SCSB. To prevent unauthorized or unintentional initialization of a full export, SCSB allows configuring the value (external.datadump.fetchtype.full) that is used as the full data dump parameter.
The resultant xml is generated as a MARCXML or SCSBXML, the schema is defined here.