SQLTXPLAIN, also know as SQLT, is a tool that helps to diagnose SQL statements performing poorly in an Oracle database. This tool is free to download and use. You only need to have access to My Oracle Support (MOS) and search for Document Id: 215187.1.
Q: What do you get from this tool?
A: In short, everything you want to know about one SQL statement if you intention is to analyze this SQL and eventually tune it. When you use this SQLT tool on a SQL statement, it generates many files then compresses them all into one zip. Always start your analysis reading the file with name sqlt_sNNNNN_main.html.