although goBoating or someone will likely elaborate on this much more, yes flatfile databases have a limited effecient storage capacity. 30,000 records sounds like it's probly above this capacity. i would definitely suggest using a better database - mySQL, Postgre, mSQL, Oracle, &c. i can't really recomend any of those over each other, but for just starting, you could give mySQL a try, as it's free to use.
HTH "If you think you're too small to make a difference, try spending a night in a closed tent with a mosquito."