This week's book giveaway is in the OO, Patterns, UML and Refactoring forum. We're giving away four copies of Refactoring for Software Design Smells: Managing Technical Debt and have Girish Suryanarayana, Ganesh Samarthyam & Tushar Sharma on-line! See this thread for details.
Can you be more elaborate about the problem you're facing? Servlets are multi-threaded; if they were developed in a thread-safe way, then concurrent DB accesses should be no problem as far as the servlet is concerned. Or are you asking about DB issues like transaction isolation?