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OCLC Support

Notes on ISBN and OCLC number expansion

Find information about ISBN and OCLC number expansion in Connexion client.
  • The OCLC number has been an 8-digit number; it now also includes 9-digit numbers to accommodate WorldCat growth. The first nine-digit number will be 100,000,000.

    The format of field 001 in OCLC MARC bibliographic records is changed starting with OCLC record number 100 million. For bibliographic records up to and including OCLC number 99999999, the 001 will continue to use the three character prefix ocm, followed by an eight digit number and a trailing space (e.g., ocm99999999).

    Starting with record number 100000000, the prefix will be ocn, the number will be 9 digits in length and have no trailing space (e.g., ocn100000000).

    The system automatically duplicates the OCLC number from field 001 in field 035 in all records output from the system, whether they are 8 or 9 digits.
  • As a result of expanding the ISBN to the new 13-digit format, when you take a final action on a record that contains an ISBN in only one format, 10-digit or 13- digit, Connexion automatically generates the other format. ISBNs are stored in 020 fields (a repeatable field).

To have the 10- or 13-digit number, whichever is not in the record, generated automatically for exported records, you must take a final action before you export; otherwise, the export retains only ISBN(s) already in the record.

A search for either the 10- or 13-digit number retrieves the record. See Technical Bulletin 253: ISBN and OCLC Number Changes for details.