how could it be a scope issue?

Without seeing the code, there really is no way to tell where the problem might lie. That's why I offered the suggestion on how you could check the problem out.

It could be that there is a leak in one of the components your using to access Oracle. The simple test there is to comment out the DB code within the loop and re-run the script. If that stops the memory growth, you know where to look. If it doesn't, you also know where.

All of which is pure speculation until you perform the test to see if memory leakage is the cause of the slowdown.

Another possibility is that you are misusing DBI. There have been examples of code here at PM where people have been preparing their statements each time around the loop, rather than once outside and then executing them inside.

Again, without sight of the code, pure speculation.