Before MVS/DFP Version 3, Release 2, the default MAXBLK size for COPYMOD was 32760. The intention was to make text blocks as long as possible to reduce the number of text blocks read to fetch the module. This often resulted in physical records created in the data set which were longer than the BLKSIZE in the data set label. (These blocks are called fat blocks.) This condition leads to I/O errors or a violation of data integrity.

Starting with Version 3, Release 2, the default MAXBLK value is the data set block size, not 32760. Further, if a MAXBLK value is specified that is larger than the block size in the data set label, then the value in the data set label is increased to the specified MAXBLK value.