All holdings come from the holding information provided by member libraries cataloging in the WorldCat database. For some databases the holdings are based on individual records holdings within WorldCat. However, for article databases, the holdings are based on the accumulated library holdings for that article’s journal.
The databases with holdings for that individual bibliographic record include WorldCat, Ebooks, GPO, SCIPIO, WorldCat Dissertations, and the Group catalogs. All these databases are getting the information from the WorldCat holdings.
The rest of the holdings information is found in article databases and that holdings information is combined from all WorldCat journal records holdings where the records containing the same ISSN as the article. Holdings for a serial are presented based on links to the current ISSN.
Specifically, journal holdings will display based on the presence of the ISSN in only the 022/a and the 776/x fields in WorldCat records. In databases such as ArticleFirst, FirstSearch will match holdings data with records based on the presence of an ISSN in the 773/x field.
If your library's OCLC symbol is attached to a journal record containing the ISSN for a journal, the symbol will be included in holdings information for that journal.