This one is pretty easy though. A customer was talking about their testing experiences with the newly added external table (ExT) functionality in Informix 11.50.xC6. He was comparing it to the standard load functions like the High Performance Loader and dbload. On almost every test, the ExT was significantly faster. However he saw that ExTs were slower was when loading from an ExT into a regular or raw table in the database. Under this scenario, the load was considerably slower.
After some quick digging around and questioning by John Miller and myself, it became clear that in doing the test, the user was dropping the table in the database, recreating it, then starting the load from the ExT. That's not a good idea. From a database perspective, when a new table is created, the engine puts some flags on it in order for it to be recovered. Those flags are removed after the first checkpoint because the database knows the create table transaction is in stable storage in the logical logs. So the user was trying to perform a a high performance load operation on a table that was trying to log every single page change in order to recover it.
So a word to the wise, if you're creating (or recreating) a table in the database as part of a ExT load operation, insert an onmode -c command before you start the ExT load commands to remove the table flags and get the fastest possible access to the table.