Suggestion: use a "last change time stamp" in both places. Keep only in
the "legal copy" data base what has been locally requested from the
"system of record" data base. Thus, the "legal copy" data base acts as a
"persistent local buffer" and contains only the needed data subset of
the "system of record data base.
It works like this:
- the "legal copy" data base (btw, same structure) is queried for
data in a table
- the "legal copy" data base has a trigger defined that reacts if
the data is there: it sends the table key and the associated "last
change time stamp" to the "system of record" data base
- if the "last change time stamp" for that key is the same,
then the "system of record" data base sends back a short message to that
effect to the "legal copy" database that will release the part of the
query that corresponds to that table.
- if the "last change time stamp" for that key is not the same,
then the "system of record" data base sends back the updated row to the
"legal copy" database that will update itself with it before it releases
the part of the query that corresponds to that table.
- if the row corresponding to the key no longer exists on the
"system of record", then the "system of record" data base sends back a
"not found" message to the "legal copy" database that will delete the
row before it releases the message to the part of the query that
corresponds to that table.
- the "legal copy" data base has also a trigger defined that reacts
if the data is not there: it sends the table key to the "system of
record" data base which sends the table row (or a "not found" message")
to the "legal copy" database that will insert it before it releases it
to the part of the query that corresponds to that table.
I hope this helps.
François
Received on Wed Jan 24 2001 - 13:14:14 CST
