IOA Access Method file allocation example

Assume the following is true for the purposes of this example:

• An Active User Report file is to be allocated on a 3390 DASD device.
• The maximum number of reports to be retained is 200,000.
• On the average, the ratio of $SYSDATA records to User Report records is 1‑to‑20.

Since the Active User Report file is to be allocated on a 3390 DASD device, the BLKSIZE parameter in the IOA Access Method file definition statement members for both the index and data components should be set to 27998. This is the maximum half track capacity of a 3390.

An additional 50 percent of the total space calculated is added as free space for block split processing.

The number of blocks to be allocated for each IOA Access Method file component is specified in the IOA Access Method file definition statement member of the component, using the SPACE parameter.

To calculate the space for the data component:

• NumberOfBlocks = [(200,000 * 300) + (200,000 * 700 * 1 / 20)]/27,998 * 1.5 = 3590
• NumberOfCylinders = 3590/2/15 + 1 =120

To calculate the space for the index component:

• NumberOfBlocks = [(200,000 * 110) + (200,000 * 110 * 1 / 20)]1/27998/*1.5 = 1240
• NumberOfCylinders = 1240/2/15 +1 = 42

Using the above formulas, the space requirement of the data component is 3590 blocks (approximately 120 cylinders on a 3390 DASD device).

Using the above formulas, the space requirement of the index component is 1240 blocks (approximately 42 cylinders on a 3390 DASD device).