In this topic:

C7.1.  Description


C7.2.  Categories of duplicates


C7.3.  Selecting the record to retain


C7.4.  Reporting duplicate records


C7.5.  Deleting records from the LC's record distributed via OCLC Connexion

C7.1.  Description

Duplicate records are two or more bibliographic records describing the same bibliographic item, ostensibly in the same manner.  Section C7.2 below describes various categories of duplicate records and identifies those that are permissible.  When duplicate records of a type not permitted are discovered, CONSER members should select one record to retain and report the duplicate record(s) to be deleted.  Section C7.3 below gives instructions on selecting records to retain, C7.4 describes the steps for reporting duplicate records, and C7.5 describes deleting records in LC's system.

C7.2.  Categories of duplicates

C7.2.1.  Latest entry records

If the only serial record for a publication is latest entry cataloging, then you may create successive entry cataloging records.  This is a category of permissible duplicate.

Do not report a latest entry record that duplicates, in whole or in part, one or more successive entry records.

C7.2.2.  LAC French cataloging

Do not report a record cataloged in French by LAC that duplicates an English language record for the same title.  This is a category of permissible duplicate.

C7.2.3.  Serials cataloged in different MARC formats

This category was once described as a permissible duplicate in the CEG, but is no longer considered permissible.  With the completion of format integration in the 1990s, all non-print serials should be cataloged using the appropriate format (i.e., leader and 008, such as sound recording, computer file, etc.).  OCLC converted most of the CONSER records to the appropriate format and merged data from non-CONSER records.  However, some duplicates may remain and should be reported to OCLC.  OCLC will change the leader (and 008) for the CONSER record and will delete the non-CONSER record.  Data, such as field 007, that appears in the non-CONSER record and is to be transferred to the CONSER record should be indicated when reporting the duplicate to OCLC.  See also instructions in Leader/06 and Fixed Fields--General Information.

C7.2.4.  Serials issued in cumulations or in parts or with supplements

LC-PCC Policy Statement 0.0, "Serial Supplements to Other Serials," "Serial Cumulations," and "Serials Issued in Part" provide guidelines for inputting separate records or for noting them on one record.  CONSER members should follow these guidelines for authenticating separate records for a serial with different frequencies, for authenticating multiple records for a serial issued in parts and for authenticating separate records for supplements to serials.

If duplicate records of these types have been authenticated, consult with the authenticating participant(s) for resolution.  For splitting into separate records entries that have been previously covered by one record, see C8. Record Consolidation/Separation.

Certain categories of duplicate records are permitted by CONSER and OCLC.

C7.2.5.  Monograph, serial, or integrating resources

Guidelines are provided in LC-PCC Policy Statement 0.0 for treatment of a publication as a serial, a monograph, or integrating resource.  CONSER members should follow these guidelines when authenticating serial or integrating resource records.  OCLC allows serial publications to be cataloged as serials or analyzed and represented by monograph records representing volumes, issues, or parts even when the parts are not uniquely titled.  Refer to OCLC's Bibliographic Formats and Standards ( for guidelines.

If LC monographic cataloging duplicates authenticated serial cataloging, report the duplication to LC (Contact the Policy and Standards Division:  Email:; Website: for resolution.  If it is decided that duplication does exist, LC will handle the deletion of the duplicate record via the MARC Distribution Service (MDS).  Deleted MDS monograph records remain in OCLC with the encoding level "J" (OCLC defined) and may continue to be used to produce cards or update holdings.  If a CONSER cataloger discovers one or more LC monographic records for a title she/he has determined to be a serial, a serial record is authenticated in OCLC and the monographic records are reported to LC.  Report to OCLC as outlined in C7.4.2. below.

If the duplication is between an unauthenticated serial record and a monograph and is not a duplication that OCLC guidelines allow (see above), report to OCLC as outlined in C7.4.2. below.

C7.2.6.  LAC microform cataloging

Do not report a microreproduction record cataloged by LAC (description based on the microreproduction) which duplicates another microreproduction record cataloged according to LC microreproduction cataloging policy (description based on the original publication).

C7.2.7.  Parallel records for language of cataloging

This is a category of permissible duplicate.  Previously in OCLC, records for the same title, but cataloged in different languages, such as English, Spanish, and French, were considered duplicate records (with the exception of LAC French cataloging discussed in C7.2.2.).  In October 2003, OCLC policy was changed to allow for parallel records within WorldCat by language of cataloging.  Now, when searching within WorldCat, if the matching record is cataloged in a language other than that used by the inputting library, the library may enter a parallel record in its language of descriptive cataloging*.  Only one record per language of descriptive cataloging will be allowed as permissible duplicate for each title.

The language of descriptive cataloging (a three-letter language code in subfield $b of field 040) is required to identify the language of descriptive cataloging.

040 ## $a MUQ $b fre $c MUQ

040 ## $a MUL $b spa $c MUL

See MARC Code List for Languages for a list of these codes.  If this subfield $b is not present in a bibliographic record within WorldCat, the language of descriptive cataloging is assumed to be English.  CONSER catalogers routinely add the 040 $b eng when authenticating or maintaining records.

The language of descriptive cataloging (field 040 subfield $b) is not to be confused with the language of the item, which is recorded in the fixed-field element Lang (Language Code) of the record.

The language of the subject headings (65X fields) is not a factor when determining the language of cataloging.

* NOTE:  The language of cataloging in CONSER records is English.  The only allowable parallel language records in the CONSER file are the LAC French/English records.

See OCLC Technical Bulletin 250 for more information on the parallel records (

C7.3.  Selecting the record to retain

Duplicate records that are not permissible according to the descriptions given above should be identified and reported for deletion.  Apply the following criteria to select the record to retain.


Select the record with the highest level of authentication:

1.   pcc $a nsdp or nlc $a isds/c

2.   pcc or nlc

3.   pcc

4.   nsdp or isds/c

5.   msc or nst

6.   lccopycat


If no records are authenticated, select the record that:

1.   Most closely adheres to RDA choice and form of entry, or

2.   The record with the most information.


If there is more than one record in the same category or subcategory, select the record input first.

C7.4.  Reporting duplicate records

If the duplicate record (not to be retained) is an authenticated record, libraries should consult and come to an agreement about whether the record should be deleted.  CONSER catalogers can optionally delete records from the CONSER database without having to notify the authenticating library if the records were input erroneously (see C7.5 below).  After the record is de-authenticated, report it to OCLC for record deletion and merging of holdings.

C7.4.1.  Reporting duplicates to LC

LC receives reports for duplicate records that are authenticated and which show LC holdings, including those for Canadian imprints, with LC holdings.  (LAC is not notified of duplicate records for Canadian serials.)  Reports may be sent via email to:  See also C7.5 below.

C7.4.2.  Reports to OCLC

If the duplicate record is unauthenticated, report it and the corresponding preferred record directly to the OCLC Quality Control Section, whose staff will evaluate the report, delete any duplicate records, and merge the holdings of the duplicate record to the preferred record.  Do not report to OCLC duplicate records that are authenticated.

Duplicate records may be reported to OCLC through the WorldCat and Authority Record Quality Control Request:  No accompanying documentation is necessary.  Participants should submit duplicate reports as frequently as possible.

C7.5.  Deleting records from the LC's record distributed via OCLC Connexion

CONSER members may delete authenticated records if they are able to determine that the record was input erroneously.  This could happen when the title is determined to be a monograph or an integrating resource or is covered by another serial record.  Report the record to LC for evaluation and deletion when LC has holdings.  Send questions about LC serials bibliographic issues and the process of deauthenticating a record to the CONSER Coordinator (

Once it is clear that the record should be deleted, the duplicate record must be deleted from the CONSER database distributed by the Cataloging Distribution Service (CDS).  Although non-LC CONSER records are no longer added to LC's local ILS, all CONSER records are distributed through CDS and duplicates must be deleted through the following steps:

1.   DO NOT remove field 010 (the 010 $a will be needed to issue the "deleted" record)

2.   Delete field 042.

3.   Add field 012 $z d.

4.   Add field 936 "RECORD REPORTED FOR DELETION--USE # ..."

5.   Replace the record and delete holdings.

6.   Report the record to OCLC for deletion.

7.   If the record is being canceled in favor of another CONSER record, record the canceled LCCN in subfield $z of field 010 in the record that is being retained.

It may be determined that the record is a valid duplicate in OCLC and can remain unauthenticated in WorldCat.  In that case, do not include field 936 "RECORD REPORTED FOR DELETION--USE # ..." nor report it for deletion, but complete the following steps:

1.   DO NOT remove field 010 (the 010 $a will be needed to issue the "deleted" record)

2.   Delete field 042.

3.   Add field 012 $z d.

4.   Replace record and delete holdings.

Related fields, etc.

Leader/06, Fixed Fields–General Information, C8

See also:

Section C.  Procedures and Instructions

CONSER Editing Guide:  Contents