Data sync uses OCLC control numbers in your records in the following ways:
- Match WorldCat records
- Link local records from local systems to WorldCat records
Because the format of OCLC control numbers has changed over many years and many local systems remove it or put it in a field other than 035, OCLC batch services uses preprocessing routines to map existing OCLC control numbers to field 035 $a, prefixed with (OCoLC).
The following table describes the changes in OCLC control numbers formatting and location over time. Records can contain any of these formats and locations for the OCLC number.
|The OCLC control number in field 001 is prefixed by ocm, ocn, or on.||
OCLC numbers 1 through 99999999:
OCLC numbers 100000000 and higher:
OCLC numbers 1000000000 and higher:
|The OCLC control number in field 035 ‡a is prefixed by (OCoLC).||OCLC number is a variable-length numeric string with no leading zeros.||(OCoLC)198765401|
Field 019 contains the OCLC control number of a deleted or merged record replaced by the current one.