recursively Adapter service invoking problem

Hello, all,

Did someone experience the problem when recusively invoking JDBC Adapter service?
My situation is: In order to process the large flat file into the DB, I recursively invoke the pub.flatFile:convertToValues() and check the ffIterator for $null, if not null, I just call the JDBC Adapter service to insert data into the DB. Now my problem is I got the [ART.114.505] error which saying “Error while invoking adapter service null”, what’s the “null” mean: input parameter is “null” or the service is “null”? And the problem happened in a random row number of flat file (sometimes 400, sometimes 500…)
Great appreciation!!