We have been designing and managing mission-critical multi-user database applications for 15 years. We have developed applications for companies large and small, from multi-national pharmaceutical companies, to regional HMOs, to smaller family-owned businesses with fewer than 100 employees. But large corporation or small business, our advice remains the same:

If your business depends upon the completeness, accuracy, and integrity of your data, then opt for a reliable CLIENT-SERVER data engine such as Microsoft SQL Server TM or OracleTM

Oracle is the better choice for a large business, SQL Server for a small business. Both database engines offer robust multi-user "concurrency" features as well as repair and recovery in the event of power loss, intermittent network service interruptions, or other kinds of common hardware failure.