Native PROC Sort performance in SAS v7-9 for Unix is not as fast or impact-neutral as you may want it to be for some very large data sets. You may not wish to use or license the default sort options SAS provides with their base Unix or Windows systems for performance or cost reasons.
SAS versions 7 and 8 for Unix support the use of IRI CoSort as an alternate sort provider with minimal installation and implementation issues. High-volume sort performance can improve up to 600% with CoSort.
SAS has not yet included IRI's CoSort extension in SAS 9.x.; however, specific requests to re-enable this affordable, high-performance sorting and file transformation engine option in the SAS environment can be made here. Please be sure to state the aforementioned reasons for wanting a direct CoSort hook, and contact your SAS representatives personally to receive a follow-up implementation estimate.
Note that you can also source and target SAS datasets via ODBC in all IRI data management and data protection software if you have that driver installed, and/or use IRI tools efficiently against flat files for SAS import/export.