Device class selection for the DEVICE option

Because RMF™ overhead is directly related to the number of devices being measured, the DEVICE option list should include only those devices that require measurement. To reduce RMF overhead further, select specific devices for reporting rather than entire device classes. In the case of Postprocessor routines, selecting specific devices can result in shorter reports, thus saving both time and paper. Storage groups are a set of DASD volumes that have been assigned one common name. By using storage groups, volumes can be grouped together in easily measurable sets. For example, assign storage groups with paging volumes separate from storage groups with excessively-used data sets.

The values you specify for the CYCLE option and the interval option also affect overhead. By decreasing CYCLE length or increasing INTERVAL length, you can increase sample size (number of samples per interval). Note, however, that decreasing the CYCLE length could significantly degrade system performance, especially in the device measurements area. Therefore, the cycle value should not be made too small, especially when the number of UCBs for measured device classes is large.