After upgrading to z/OS 2.5, 3.1, or 3.2, issues might occur with DFSMS‑controlled data sets that are allocated by SAS without explicitly specifying DCB attributes for BLKSIZE.

In these environments, z/OS uses System‑Determined Blocksize (SDB) to automatically calculate an optimal block size when BLKSIZE is omitted.

Symptoms

When SAS allocates a new data set without a BLKSIZE value, the following symptoms occur:

• The BLKSIZE shown in SAS step statistics does not match the BLKSIZE displayed in ISPF 3.4 or by other z/OS utilities.
• Subsequent z/OS programs that read these SDB‑allocated files might fail with the following abends or other:

S013‑34

S002‑30

These abends occur because the BLKSIZE determined by SDB is not always compatible with programs that expect traditional BLKSIZE values.

Workaround

IBM has released Program Temporary Fixes (PTFs) to correct this behavior. Apply the appropriate fix for your z/OS release:

z/OS Release	PTF
2.5	UJ97198
3.1	UJ97197
3.1	UJ98495

Install the relevant PTF to ensure consistent BLKSIZE handling for SAS‑allocated DFSMS data sets and prevent the abends described above.