Can an Oracle 19c database dblink to an Oracle 10.2.3 database?
Based on this document from Oracle Support, the answer appears to be &quot;No&quot;. A 19c client (the owner of your DB Link) is only supported/compatible with a server version of 11.2 or greater.
Conversely, a 10.2 database can only support a client as new as 12.1, so any upgrade of your 12.1 database to any newer version will break your db link.