019 overlay and index question

[Yuan Yao <yaoy at law dot georgetown dot edu>]

In addition to 001 field, many OCLC records have another control number 
field, 019, which is duplicate records that have been deleted from 
WorldCat and replaced by the present record.

I have two questions related to this 019 field:

When loading such a record into Innopac and overlaying an existing 
record with 001 field only,  is it possible to have the system compare 
001 in both the incoming and existing records first, then,  if they 
don't match, compare the value in incoming 019 with that of 001 in 
existing record?

We keep both 001 and 019 in our records, and our index rules list both 
as OCLC # (o).  However,  the value of 019 is not searchable as OCLC 
number.  Any comment or suggestions?

Thanks,

Yuan Yao
Head of Cataloging
Georgetown University Law Library