Why do we code BLKSIZE=0 in JCL At our mainframe shop, there are many jcl’s which use BLKSIZE=0 for the datasets which are cataloged by the JCL. From what I learnt during my training the BLKSIZE has to be a multiple of and would mean the number of logical records to be clubbed in a physical record to make one block of I/O But if we use BLKSIZE of zero, will this mean that the file is not blocked or the system would block the file on its own? “; ; ; ;