We have an Oracle 11gR2 EE server. The server is Windows 2008 R2 with 1.2 TB of free space, and 24 GB of memory. We are running a lots of SQL scripts regularly on the server. Those scripts insert data from a set of tables in one schema to another set of tables in a different schema. Insert statements in scripts are always like: Insert into ... select ... from. Sometimes we use nested queries, joins and Oracle functions in select part. Recently we have had a performance problem and realized that Insert statements with joins from more than one table are extremely slow. Insert statements with no joins have no problem. Our joins are mostly inner joins from one or two tables. What can be the problem?