title: What is the best default transaction isolation level for an ERP, if any?
body: <p>Short background: We are just starting to migrate/reimplement an ERP system to Java with Hibernate, targeting a concurrent user count of 50-100 users using the system. We use MS SQL Server as database server, which is good enough for this loads.</p>
  
  <p>Now, the old system doesn't use any transactions at all and relies for critical parts (e.g. stock changes) on setting manual locks (using flags) and releasing them. That's something like manual transaction management. But there are sometimes problems with data inconsistency. In the new system we would like to use transactions to wipe out these problems.</p>
  
  <p>Now the question: What would be a good/reasonable <strong>default</strong> transaction isolation level to use for an ERP system, given a usage of about 85% OLTP and 15% OLAP? Or should I always decide on a per task basis, which transaction level to use?</p>
  
  <p>And as a reminder the four transaction isolation levels: READ UNCOMMITTED, READ COMMITTED, REPEATABLE READ, SERIALIZABLE</p>