Ljubomire, you can disable commit.lock, but you should not need to. The fact that you are running into locking issues indicates that your code is a bit buggy. Disabling the locking in that case especially, would most likely result in exceptions. You can have multiple index reads (querying), you can even query the index while writing to it, but you must only have a single IndexWriter adding or deleting documents from the index at any one time.
Your code most likely has multiple IndexWriters accessing the same index simultaneously, and that is why you are running into locked index issues.