Statistics Files

The default and minimum configuration uses two such file pairs, making four VSAM files. The maximum number of file pairs you can use is twenty. Specify the number of file pairs and the VSAM cluster names with the STAT.DSN.BASE and STAT.FILE.PAIRS initialization parameters.

The RECORDS parameter of the Access Methods Services DEFINE command for the ESDS cluster specifies the maximum number of records each file pair can contain. The maximum number of statistics records available is the sum of the values in the RECORDS parameters for all the statistics ESDS clusters. For example, if you determine that your system needs space for 15,000 statistics records, you can define three file pairs containing 5,000 records each, or two file pairs containing 7,500 records each.

Within each file pair, Sterling Connect:Direct writes statistics records to the ESDS cluster. Sterling Connect:Direct uses the KSDS cluster to maintain index information about the records in the ESDS. Whenever either file of the pair becomes full, the entire pair is considered full, and the system initiates a switch to the next pair in the sequence. Because the file pair is full when one file fills to capacity, it is important that you size the ESDS and KSDS in a file pair appropriately, relative to each other. Specifying appropriate file sizes reduces the waste of excessive space.

The frequency with which Sterling Connect:Direct writes records to the KSDS cluster of a file pair depends on usage patterns at each site. On average, Sterling Connect:Direct writes one KSDS record for every two statistics records written to the ESDS cluster. For best results, make the size of the KSDS cluster in records about 75 percent of the number of ESDS records.

The following table shows the default VSAM control interval sizes for the statistics files.

The values in the table are the optimal control interval sizes. The only Sterling Connect:Direct requirement is that the CI size of the ESDS data component must be a minimum of 2,048.

The default configuration provides space for 13,500 statistics records evenly divided between two file pairs. The minimum configuration provides space for 2,000 statistics records. The amount of activity in the Sterling Connect:Direct system determines how frequently the statistics file pair list wraps around. Estimate your activity rate and allocate enough space so that the system records several days of records before a wraparound occurs. After running Sterling Connect:Direct for several days, you may need to adjust the number or sizes of the statistics files to allocate the right amount of space.