A naive approach to inserting 100 000 rows in the database using Hibernate might look like this: This would fall over with an OutOfMemoryException somewhere around the 50 000th row. That's because Hibernate caches all the newly inserted Customer instances in the session-level cache. In this chapter we'll show you how to avoid this problem. First, however, if you are doing batch processing, it is absolutely critical that you enable the use of JDBC batching, if you intend to achieve reasonable performance. Set the JDBC batch size to a reasonable number (say, 10-50): You also might like to do this kind of work in a process where interaction with the second-level cache is completely disabled: When making new objects persistent, you must flush() and then clear() the session regularly, to control the size of the first-level cache. For retrieving and updating data the same ideas apply. In addition, you need to use scroll() to take advantage of server-side cursors for queries that return many rows of data.