These two fields are invariably used together in their own unique record. Field #0ry is used to link a piece record with the main record of which it is a piece, and field #899 contains the shelfmark together with the number or name of the piece (if there is one) in subfield |v, and the barcode in subfield |b. There must be one piece record for each individual piece, and the record may contain only the two fields #0ry and #899 (apart from #000 and #0rr of course).
When the first piece record is created, the software will automatically reproduce the unique record number of the main record (in its #000 field) in the link field (#0ry) of the piece record, together with the default link identity +bod001. Second and subsequent piece records (if any) are produced by copying the first record and altering the variables (that is, the contents of subfields |v and |b):
The following index extract shows how piece records cohere:
Of the work in question (the first edition of 中國叢書綜錄, 3 volumes), there are two copies in the Book Storage Facility and one in the China Centre Library. Note how the pieces are numbered. If there were a third copy in the Book Storage Facility the link identity would be +bod007 &c, and if there were a second copy in the China Centre Library the link identity would be +ccl004 &c.