AttemptMaxRows is a transaction timeout behavior that works like this.
In order for a transaction to be ended (Commit or Rollback) there should not
be any open cursors. So, one of the things IBO attempts to do for you in
order to allow a transaction to be ended transparently is to fetch records
in a dataset looking to get to the end of it. If it can get to the end of
all datasets then it can release the handle to the server. In some cases you
may want to put a limit to the number of records it will pull in while
trying to get to the end of the records.

HTH,
Jason Wharton
CPS - Mesa AZ
http://www.ibobjects.com