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Once you've located the data directory, you can look for the files that comprise the PostgreSQL database server. The layout is as follows:

None of the aforementioned directories contain user-modifiable files, nor should any of the files be manually deleted in order to save space, or for any other reason. Don't touch it, because you'll break it, and you may not be able to fix it! It's not even sensible to copy files in these directories without carefully following the procedures described in Chapter 11, Backup and Recovery. Keep off the grass!

We'll talk about tablespaces later in the book. We'll also discuss a performance enhancement that involves putting the transaction log on its own set of disk drives in Chapter 10, Performance and Concurrency.

The only things you are allowed to touch are configuration files, which are all *.conf files, and server message log files. Server message log files may or may not be in the data directory. For more details on this, refer to the next recipe Locating the database server's message log.