Functional Overview

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# Functional Overview

The INVERT function:

- modifies the field definition table (FDT) to indicate that the specified field is a descriptor; and

- adds all values and corresponding ISN lists for the field to the inverted list.

The newly defined descriptor may then be used in the same manner as any other descriptor. This function may also be used to create a subdescriptor, superdescriptor, phonetic descriptor, or hyperdescriptor.

The COUPLE function adds a common descriptor to two files (updates their inverted lists). Any two files may be coupled provided that a common descriptor with identical format and length definitions is present in both files. A single file may be coupled with up to 18 other files, but only one coupling relationship may exist between any two files at any one time. A file may not be coupled to itself.

Note
Only files with numbers 255 or lower can be coupled.

Changes affecting a coupled file's inverted lists are automatically made to the other file. The DBA should consider the additional overhead required to update the coupling lists when the descriptor used as the basis for coupling is updated, or when records are added to or deleted from either file. If a field that is not defined with the NU option is used as the basis for coupling and the field contains a large number of null values, a considerable amount of additional execution time and required disk space to store the coupling lists may result.

An interrupted ADAINV operation can be restarted without first having to restore the file.

The ADAINV utility requires that the nucleus be active. If the nucleus is canceled (terminated) while the ADAINV utility is running, all the work performed at that point is lost. This is because the FDT and the FCB have not been rewritten to include the new descriptor. The rewrite occurs at the very end of processing and is triggered by a special Adabas call sent by ADAINV.