java general question(transaction realted)

Hi consider i have developed a web based application. i have a page which will update an employee salary. my application is running. suppose consider two manager opened edit page to edit the employee salary. one manager thought to increase 3000$, and another manager thought to minus 2000$. the page is opened by two manager. 'Edit salary' page a combo box that will accept the new salary. not the increment value. both the managers see 10000$ in their edit page. first manager update it to 12000$ and he submitted it. transaction completed. Second manager don't know the previous edition. so he is having the old value which is 10000$. so he is changing it to 9000(minus 1000$).

But actually it should be 11000$. how to solve this problem?

Transaction-based database access?

And welcome to JavaRanch