I just dumped the contents of ALL_OBJECTS to a worksheet as INSERT statements. It grabbed about 100k records in about 5 or 6 seconds.
Does CSV or DELIMITED or LOADER give you similar performance issues?
It is a not a consistent problem it seems.
Anything in particular I should look when it happens again?
Could it be memory related?
If no heavy-duty processing that may interfer is occurring on the client or server (if applicable), then the most logical culprit is hitting the JVM's virtually memory limit and the resultant garbage collection overhead that ensues.
Just to give you an idea, in terms of normal performance, the behavior for exports on any modern laptop and locally networked server should be at least 2,000 rows/sec, or at least 500 rows/sec when using a server with a latency of around 50 milli-seconds.