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Postby Arkantos » Fri Jun 11, 2010 2:56 pm

Is ISN a logical identifier or a Physical Identifier.

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Postby RGZbrog » Fri Jun 11, 2010 10:10 pm

Logical. It's a pointer to a physical block.

Within the Associator, the Address Converter (AC) is a list of 3- or 4-byte pointers to Adabas data blocks (Relative Adabas Block Number, or RABN - pronounced "robin"). A record's ISN is a pointer into the AC to the associated Adabas block.

For example, when you execute the Natural statement
GET file 12
the RABN in the 12th entry of the AC is used to retrieve the Adabas data block which contains the record.

A record's RABN may change, but it's ISN does not.
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