You enter data into the system input stream by preceding it with a DD * or a DD DATA JCL statement. This is called a SYSIN data set. The DD name is not necessarily SYSIN.

A SYSIN data set cannot be opened by more than one DCB at the same time; that would result in an S013 ABEND.

If no record format is specified for the SYSIN data set, a record format of fixed is supplied. Spanned records (RECFM=VS or VBS) cannot be specified for SYSIN.

The minimum record length for SYSIN is 80 bytes. For undefined records, the entire 80-byte image is treated as a record. Therefore, a read of less than 80 bytes results in the transfer of the entire 80-byte image to the record area specified in the READ macro. For fixed and variable-length records, an ABEND results if the LRECL is less than 80 bytes.

The logical record length value of SYSIN (JFCLRECL field in the JFCB) is filled in with the logical record length value of the input data set. This logical record length value is increased by 4 if the record format is variable (RECFM=V or VB).

The logical record length can be a size other than the size of the input device, if the SYSIN input stream is supplied by an internal reader. JES supplies a value in the JFCLRECL field of the JFCB if that field is found to be zero.

The block size value (the JFCBLKSI field in the JFCB) is filled in with the block size value of the input data set. This block size value is increased by 4 if the record format is variable (RECFM=V or VB). JES supplies a value in the JFCBLKSI field of the JFCB if that field is found to be 0.