Working storage utilization

The total working storage and the ratio of the number of one size block to another will vary from system to system. These parameters are adjustable and established at system initialization time. The number of blocks assigned to each pool is also printed on the System Summary Report.

In the System Summary Report, block occupancy (utilization) is expressed in two forms. The minimum, maximum, and mean block occupancies are expressed as decimal fractions (blocks in use or blocks allocated). Mean available block figures are the average of the actual number of blocks allocated but unused. As with all data collection variables, block occupancy must be related to other variables in order to be meaningful.

For each block size, the mean number in use multiplied by the number of bytes per block equals the mean bytes per pool in use. When the sum of all pools is divided by the number of active messages (as shown in the System Summary Report) the amount of working storage used on a per-message basis should approach system design criteria. Any great variance should be investigated.

Example: Assume that the ECB Block Occupancy is 10% and Idle Occupancy at Level 1 is quite high. Level 1 indicates that the system is not servicing the input list because of an insufficient number of available ECB blocks, yet the ECB pool is only 10% utilized. This indicates that the CPU loop parameter stating the number of ECB blocks that must be available is set too high, or the system is experiencing very unusual peaking conditions that are not reflected in mean utilization of the working storage pool.