Currently the API to update contacts only updates one record, even if the sync field matches more than one record. The Acoustic database allows duplicates records, but the API will only update one of those records (the oldest one, based on what the Acoustic rep told me). For example, in a request like:

<CREATED_FROM>1</CREATED_FROM> <UPDATE_IF_FOUND>true</UPDATE_IF_FOUND> <SYNC_FIELDS> <SYNC_FIELD> <NAME>USERID</NAME>

<VALUE>2308533</VALUE> </SYNC_FIELD> ...

Even though more than one record exists with userid: 2308533, only one will be updated.

This is causing major problems with our mailings, due to only one record being updated, instead of all records matching userid 2308533.

Acoustic allows for duplicate records, yet doesn't allow the API to manage those records properly. We need this data managed in real time via API and uploading batch updates is not an option.