This section will explain each of the values printed next to the graphic display. Those columns that were described in preceding sections will only be summarized at this point.
This is the relative byte address of the start of the control area that this index CI controls. This number is used by the VSAM access method to determine where the data corresponding to the keys in this index starts. This value is provided for informational purposes only.
This is the number of free control interval pointers that exist in this particular index control interval. In other words, this number represents the number of data control intervals that are not being used in the corresponding data control area.
This is the number of pointers being used in this index CI. This corresponds to the number of data control intervals being used in the control area. This value, added to the FREE PTRS value, is the same as the number of control intervals per control area in the data component.
This is the number of empty bytes or characters in the index control interval that can be used to hold pointers to the data control area. This value was discussed previously.
The average number of bytes required to hold both the control information and compressed data key for each control interval being referenced in this data control area.
The average length to which each data key compresses, excluding any system control information.
The number of unreferenceable data control intervals in this control area. The following paragraph describes this value in detail. If this value is not zero, DASD space is being wasted. If this number is large, redefine the cluster with different control interval sizes.
This value represents the relative order of the control area in key sequence. In a cluster that has had no control area splits; this value should always be incremented by one for each line in the graph.
This value represents the relative deviation between the current control area and the one that preceded it in key sequence. In an organized cluster, this value will be 1. Since this value is normal, it is suppressed on the report so you will see blanks instead. If the value is other than 1, the control area does not physically reside next to the control area beneath it in key sequence. What does this mean? Assuming a control area size of one cylinder (the optimal value for most clusters), the arm that reads the data on DASD has to move the number of cylinders shown under the REL DEV column to read the data in keyed sequential mode. If the number printed has a - after it, the seek would be backwards. It is important to understand that this number has no relevance when the cluster is accessed in direct key mode, since the index is searched to find where the record resides (such as in online databases). But if the file is accessed in keyed sequential mode—as CA Disk does to produce a backup copy of the data set— then the head movement can have a negative impact on the performance of the read operations.
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