Apparently you use a database link in your query/insert/update. And probably you use an XA datasource.
FIrst of all I'd try to prevent using a database link in your queries or DML used from SOASuite. Think about it. SOA Suite is an integration tool, to integrate applications and datastores. Every database or every (set of) application service(s) should be seen as an application to integrate. You want loose coupling between the applications.That is the whole point behind the use of tools like SOA Suite, OSB, Tibco, Mulesoft, etc.
But now you create a Database Link between two databases. I figure that those are two databases servicing two different application. What you do using a database link is making those application-databases interdepent from out side SOASuite or OSB. And using a database adapter you try to query that.
The pattern should actually be that you query one database for triggering events, and then enrich the data with data from the other database from within SOASuite and then transform that. What you do is the enrichment outside SOASuite.
In your case you should check the db-link if it is public and/or shared. Get help from a DBA for instance. Then also try the same using another Database Adapter config, using a non-XA-datasource. But again, as layed out above, preferably don't use a db-link at all.