[OPEN-ILS-DEV] TCN value question related to Keeping bib / auth / MFHD / record identifiers in sync post

[Alan Rykhus]

Hello,

I've read the 4 posts related to the Dan Scott's post on keeping the 001
field in sync with the EG record_entry id and it brings up a question
for me.

What exactly is the real purpose of the tcn_source and tcn_value columns
in the biblio.record_entry table?

I'm working on some conversion scripts and the one thing I am looking at
changing in the current conversion scripts for loading records is to let
the system generate the biblio.record_entry.id value and to store the
previous system's record id in the biblio.record_entry.tcn_value field. 

The current scripts populate the id and tcn_value with the old system's
records id. My reasoning for changing this is that I can see bringing in
records from different systems where these values would collide. An
additional concern is that you convert some libraries into Evergreen,
they run on it for a while, then you add additional libraries, bringing
in new bibs, and again you might have biblio.record_entry.id collisions.
If I let the system generate the ids, and store the old id in the
tcn_value, I can use sql to find out the current bib id, which is needed
to generate asset.copy(actually asset.call_number) entries and their
related links.

thanks -- al
-- 
Alan Rykhus
PALS, A Program of the Minnesota State Colleges and Universities 
(507)389-1975
alan.rykhus at mnsu.edu