Is SQL*Net message from dblink > 30% a performance issue? I have a Java web-application running under Glassfish. App accesses Oracle using JPA (eclipselink).

Last 2 days I'm observing some perfomance issues: some messages about long running queries (10 to 100 sec) appears in Glassfish logs.

I asked Oracle DBA to provide Oracle AWR-log for 2 hours. There's SQL*Net message from dblink in top 5 Timed foreground events. It's seems suspicious for me, am I right, that in normal case there shouldn't be SQL*Net message from dblink in top 5 Timed foreground events? Is it a perfomance issue with database on the dblink other side?
Most likely means that the the shadow process(es) that support the dblink connection(s) are idle. Well they are definitely idle. The only question is are these idle periods between cursors or within an executing cursor. If they are within an executing cursor then whatever is driving the cursor execution, the fetching, is slow. But odds are it's simply an idle dblink connection. See http://kylehailey.com/oracle-sqlnet-wait-events/