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Demonstration 6

The previous 3 demonstrations all failed with a SPACE related issue so that influenced thinking, especially as BLKSIZE=0 indicates System Determined BLKSIZE (SDB) and z/OS is supposed to assign the optimum BLKSIZE.

However, look at RECFM. In the previous demonstrations it was coded RECFM=F and the absence of the B meant that there would only be 1 record per block.

A track can only hold 78 sixty byte blocks, and as a cylinder is 15 tracks it can only hold 1170 blocks (78 * 15).

Remember the 16 extent per volume limit for non-VSAM data sets is a further restriction.

Demonstration 6 - results in COND CODE 0000

Changing to RECFM=FB, will mean that BLKSIZE=0 equates to BLKSIZE=27960, with each block holding 466 records. A track can accommodate two 27,960 blocks, i.e. 932 records (466 * 2). Two tracks will hold 1864 sixty byte records which exceeds our requirement of 1398.

View a 3390 track capacity chart.