Expansion of OCLC Control Number

You've heard it before, but I am bid to remind you again. OCLC Control Numbers are expanding in July 2013. Here's the scoop:

WorldCat continues to grow! As indicated earlier this year, the OCLC Control Number is anticipated to reach one billion after July 1, 2013. At that point, OCLC will increase the length of the OCLC number to accommodate a variable length number string. If you use and/or store OCLC MARC bibliographic records and the OCLC Control Number, you will notice a change after July 1, 2013. You will need to check the systems at your institution that use OCLC MARC bibliographic records and the OCLC number. You may need to implement changes to ensure those systems will be able to successfully handle the longer OCLC number effective July 1, 2013.

For example, libraries may be impacted in the following areas:

• Cataloging and IT librarians that download OCLC MARC bibliographic records to the library’s local system
• Resource sharing librarians using third party ILL management programs that store or use the OCLC number for searching
• Reference services librarians using WorldCat Local to help a patron locate an item

Publishers, vendors and others that partner with OCLC may be impacted as follows: 

• Integrated Library Service (ILS) vendors that use OCLC MARC bibliographic records to test compatibility with OCLC
• Publishers, material suppliers and electronic content providers that use OCLC MARC bibliographic records in their systems 
• Developers maintaining services that use OCLC Control Numbers

Format of the OCLC Number

The OCLC Number resides in the MARC 001 field and may also be stored in other fields.  The OCLC Number in the 001 field is formatted as follows:

OCLC numbers 1 through 99999999:

• “ocm” prefix
• oclc control number, 8 digits, right justified with leading zeros
• A blank space as the last character
  Example: ocm00012345

OCLC numbers 100000000 to 999999999:

• “ocn” prefix
• oclc control number, 9 digits
  Example: ocn123456789

OCLC numbers 1000000000 and higher:

• “on” prefix
• oclc control number, 10 or more digits
  Example: on1234567890 or on1234567890123

In the 035 field, the OCLC number is usually stored with the prefix (OCoLC) and without the “ocm”, “ocn” or “on” prefixes; for example: (OCoLC)1234567890.

When this change takes place

The “on” prefix will be used to identify OCLC Numbers that contain ten or more digits.  Nine or eight digit OCLC Numbers will continue to use the “ocn” or “ocm” prefix as described above.  The update to the OCLC Number is backwards compatible so that previously defined OCLC Numbers will not be impacted.  Previously assigned OCLC Numbers will continue to work as before.

What action should you take?

If you use and/or store OCLC MARC bibliographic records and the OCLC Control Number, you will notice a change after July 1, 2013. You will need to check the systems at your institution that use OCLC MARC bibliographic records and the OCLC number.  You may need to implement changes to ensure those systems will be able to successfully handle the longer OCLC number effective July 1, 2013.

Sample records

OCLC plans to make a file of sample MARC bibliographic records containing the new, expanded numbers available for download on the OCLC Control Number Expansion website before the end of the calendar year 2012. When the file becomes available, announcements will be widely posted in the same places this notice is being posted.  Anyone may then download the file for use in testing their systems.

For more information

Additional technical information regarding this change is available here.  Please visit the Web to learn how OCLC Control Numbers are created and how OCLC Batchload services give libraries the ability to match, merge, format and synchronize OCLC Control Numbers between their local systems and WorldCat.  To see new OCLC Control Numbers when they are assigned, visit Watch WorldCat Grow.  If you have questions, please contact us at support@oclc.org or 1-800-848-5800 (USA) or 1-614-793-8682.