COBOL's FASTSRT compile-time option is a special feature of the language that can improve performance for qualifying applications which use the COBOL SORT statement. You should always specify the FASTSRT option. COBOL decides automatically at compile-time whether FASTSRT can actually be used. For example, FASTSRT cannot be used for input processing when an INPUT PROCEDURE is specified. See the appropriate COBOL guide for the complete list of FASTSRT requirements and restrictions.

When FASTSRT is in effect for input processing, COBOL passes the ddname of the input data set to DFSORT. DFSORT uses this ddname to read the input data set directly.

When FASTSRT is in effect for output processing, COBOL passes the ddname of the output data set to DFSORT. DFSORT uses this ddname to write the output data set directly.

Input or output processing by DFSORT rather than COBOL can result in reductions in CPU time, EXCPs, and elapsed time.