Functional Overview

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# Functional Overview

The ADAMER utility produces statistics that indicate the number of Data Storage accesses required to find and read a record when using an ADAM descriptor. This information is used to determine

- whether usage of the ADAM option would reduce the number of accesses required to retrieve a record using an ADAM descriptor as opposed to the standard Adabas accessing method;

- the amount of Data Storage space required to produce an optimum distribution of records based on the randomization of the ADAM descriptor.

The input data for ADAMER is a data set containing the compressed records of a file produced by the ADACMP or ADAULD utility.

The field to be used as the ADAM descriptor is specified with the ADAMDE parameter. A multiple value field or a field contained within a periodic group may not be used. The ISN assigned to the record may be used instead of a descriptor as the basis for randomization (ADAMDE=ISN parameter).

The ADAM descriptor must contain a different value in each record, since the file cannot be successfully loaded with the ADAM option of the ADALOD utility if duplicate values are present for the ADAM descriptor. The ADAMER utility requires a descriptor field defined as unique (UQ), but does not check for unique values; checking for unique descriptor values is done by the ADALOD utility when loading the file as an ADAM file.

The BITRANGE parameter may be used to specify that a given number of bits are to be truncated from each ADAM descriptor value before the value is used as input to the randomization algorithm. This permits records containing ADAM descriptor values beginning with the same value (for example, 40643210, 40643220, 40643344) to be loaded into the same physical block in Data Storage. This technique can be used to optimize sequential reading of the file when using the ADAM descriptor to control the read sequence, or to remove insignificant information such as a check digit.