About record structure

Find an overview of the record structure, including content designation and repeatability, of OCLC MARC records.

"Record Structure" describes the general structure for the leader, the directory, and the control and variable fields in OCLC-MARC bibliographic and authority records.

OCLC-MARC format

OCLC-MARC formats are sets of codes and content designators defined for encoding particular types of machine-readable records. They serve as the vehicle for bibliographic and authority data for all types. The formats provide specifications for the exchange of information between systems.

Additional information on OCLC-MARC format

For descriptions of the OCLC-MARC bibliographic and authority records, see Bibliographic Formats and Standards and Authorities: Format and indexes.

Content designation

Content designation identifies and characterizes the data elements that comprise OCLC-MARC records.

Tags and fields

OCLC-MARC records are organized into fields identified by three-character numeric tags
The tag is stored in the directory entry for the field, not the field itself
Fields are grouped into blocks according to the first character of the tag, which generally identifies the function of the data in the record
The type of block varies with each type of record: bibliographic or authority

Bibliographic record blocks

Bibliographic records have the following blocks:

0xx Control information, numbers, and codes 1xx Main entry
2xx Titles and title paragraph 3xx Physical description, etc. 4xx Series statements
5xx Notes
6xx Subject access fields
7xx Added entries other than subject or series; linking fields 8xx Series added entries, location, and alternate graphics 9xx OCLC-defined local fields

Authority record blocks

Authority records have the following blocks:

0xx Control information, numbers, and codes 1xx Heading
2xx Complex see references
3xx Complex see also references
4xx See from tracings
5xx See also from tracings
6xx Reference notes, treatment decisions, notes, etc.
7xx Heading linking entries
8xx Location and alternate characters
9xx OCLC-defined local fields

Repeatability

All fields are theoretically repeatable
The nature of the data in the fields, however, may preclude repetition
Examples of nonrepeatable fields include 001 (Control Number), 005 (Data and Time of Latest Transaction), and field 245 (Title Statement)
OCLC-MARC Records specifies the repeatability (R) or nonrepeatability (NR) of each field and subfield in the lists of content designators

Coded data

OCLC-MARC formats include specifications for data elements represented by coded values
Coded values consist of fixed-length character strings
Elements within coded-data fields or subfields may be identified by relative character position
Although coded data occurs most frequently in the leader, directory, and variable control fields, any field or subfield may be defined for coded data