Mistake Mistake

The multithreaded Java application I wrote in April 06 for extracting data from 90k files to IBM DB2 v8.2 system suffering from performance bottleneck when dealing with too many worker threads. This is a common issue for multithreading programming and that's why we got something called Thread Pool. While waiting for the extraction to be finished (God, it has been running for 30 hours and still executing at this moment), I took some initiatives to perform a code review, trying to identify possible programming faults. And oh yeah, found a potential program problem. See figures below




What you think is wrong with the above code snippets? Well, I try to recall the rationale of doing the stuff like that when I was developing this program and I think I did that to avoid the intricacy of thread synchronization due to very constrained assigned time frame.

I wouldn't tell you what's wrong with it and I hope you can spend some time exploring it out. However I can tell you that one of the way to get out from this scalability issue is to using java.lang.ThreadLocal to manage the connection instead.