The specifications for transferring files of MARC 21 records electronically assume the use of a standard protocol. The File Transfer Protocol (FTP) is the most generally used. FTP can be used in place of a physical exchange medium to move MARC 21 authority, bibliographic, classification, community information, and holdings records from a storage device in an originating system to a receiving system. These electronic file transfer specifications were approved by the Library of Congress and the MARC 21 Advisory Committee in June 1993, and by the Canadian Committee on MARC in October 1993.
The labels used with electronic file transfer, like tape and diskette volume and file labels, communicate information from the originating system to the receiving system. The labels identify and characterize the transaction and the information contained in the data that is being transferred electronically. The labels will make possible an eye-readable display of the identifying information and also enable machine processing of the information.
Each file of MARC 21 records should be accompanied by a companion label file containing bibliographic file and volume information. The label and record file pair can be transferred separately or they can be compressed (archived) into a single file for transfer by the originating system. It is then up to the receiving system to decompress (restore) the label and record file(s). The concept of physical volumes does not apply to electronic transfers as it does to exchange using dismountable physical media, but the identification of volumes may be particularly useful with groups of files compressed for transfer into a single file. Record blocking is not used and individual records do not span files or transfers. Large logical files of records can be segmented into multiple physical files during separate transfers. The following configurations may be used.
Uncompressed transfer Compressed transfer Label File Compressed File Bibliographic File Label File 1 Bibliographic File 1 Label File n Bibliographic File n
A file of MARC 21 records is transferred electronically following a label file that identifies and characterizes the file of MARC 21 records, and optionally, the volume to which it belongs. NOTE: Volume information is not transmitted in a separate file as is done with tape and diskette. The label file is used to transfer non-MARC information between an originating system and a receiving system. The label file is written using only ASCII Latin characters. A label file is required for each file of MARC 21 records transmitted.
These MARC 21 specifications do not mandate the length or style of file names due to differences between operating systems. Exchange partners should agree upon file naming conventions prior to transferring MARC 21 records electronically.
A label file consists of a sequence of fixed-length and variable fields. The order of fields should be the same as the list below. The length of fixed-length fields is specified in the descriptions of those fields. Variable length fields have no maximum length. Each field in a label file begins with a three-character tag followed by two blanks (ASCII character 20 (hex)). The field's data content follows the two blanks. Each field ends with a carriage return (ASCII control character 0D (hex)) or a carriage return/line feed pair (ASCII control characters 0D 0A (hex)) immediately following the data in the field. The field terminator character (ASCII control character 1E (hex)) is no longer used.
Certain fields in the label files are specified as mandatory and must be present in each label file. In these fields, data content or one fill character (the vertical bar | (ASCII character 7C (hex)), must be supplied. Mandatory or optional characteristics of the fields are also noted below. Several of the fields are repeatable.
The following order of the fields in the file label is mandatory whether or not all fields are present.
Mandatory Fixed/ Repeat- Tag Element Name Description /Optional Variable able DAT Date compiled YYYYMMDDHHMMSS.F M F NR RBF Number of records Numeric M V NR DSN Data Set Name Alphanumeric M V NR ORS Originating sys ID Alphanumeric M V NR CID Country ID Alphanumeric O F NR DTS Date sent YYYYMMDDHHMMSS.F O F NR DTR Dates of records YYYYMMDDYYYYMMDD O F NR FOR Format Alphanumeric M F NR FQF Format qualifier Alphanumeric O V NR DES Description Alphanumeric O V R CS0-n Character set 0-n Alphanumeric O V NR CV0-n Set variations 0-n Alphanumeric O V R VOL Volume Alphanumeric O V R ISS Issue Alphanumeric O V R FDI Final Dest. ID Alphanumeric O V NR REP Reply to Alphanumeric O V R NOT Note Alphanumeric O V R
Each file is transferred electronically as a separate operation. If no compression is involved, a label file should be transferred preceding the MARC 21 record file to which it relates. If label and record files have been compressed, the transfer of all data can occur as a single operation to the receiving system. In this case, the receiving system must process the compressed file to restore the label and record file(s) as separate files.
Example of an electronic file transfer label file:
DAT 19940311141236.0 RBF 1564 DSN LOC.BOOKS.DIST.DATA.D940311 ORS DLC DTS 19940312083152.0 DTR 1994010119940230 FOR M DES MDS-Books All VOL V21 ISS 1XX
MARC 21 HOME >> Specifications >> Exchange Media > > Part 1
|The Library of Congress >> Especially
for Librarians and Archivists >> Standards
( 12/06/2007 )