LRECL specifies the length, in bytes, of each record in the data set. If the records are of variable length or undefined length, the maximum record length must be specified. For input, the field has no effect for undefined-length (format-U) records. The value of LRECL and when you specify it depends on the format of the records:

• For fixed-length unblocked records, LRECL must equal BLKSIZE.
• For PDSEs or compressed-format data sets with fixed-length blocked records, LRECL must be specified when the data set is opened for output.
• For the extended logical record interface (XLRI) for ISO/ANSI variable spanned records, LRECL must be specified as LRECL=0K or LRECL=nK.