bdfd1m1l | Database Administration |
The following scenario addresses setting different sizes for overflow blocks.
Nearly all (90%) of the subfiles in a file contain about 1200 bytes. The remaining subfiles are much larger, each containing approximately 5000 bytes.
You do not want to allocate 4095-byte overflow blocks because this means that most (90%) of the overflow blocks will have 2895 bytes of wasted DASD space.
In this example, set the prime block size (&SW00WRS) to L2, the overflow block size (&SW00ARS) to L4, and set &SW00OP1,#BIT5.
The &SW00OP1 indicator tells the TPFDF product to process overflow blocks in an economical way. If the overflow data fits into blocks the same size as the prime blocks (L2), the TPFDF product will use overflow blocks of this size. This is an economical solution for the 90% of the subfiles that contain about 1200 bytes.
If the TPFDF product cannot fit the overflow data into these small blocks, it uses overflow blocks of a size specified by the &SW00ARS set symbol. In this example, the larger subfiles (10%) use 4095-byte blocks (size L4).
&SW00WRS SETC 'L2' &SW00ARS SETC 'L4' &SW00OP1 SETC '.....1..' (bit 5 set)
No changes are necessary if the changes are made in the DSECT macro.