IBM Mainframe Forum

Is ISN a logical identifier or a Physical Identifier.

Regards
Arkantos

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 statementthe 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.