Oracle Database 11g Release 2 is out, and as usual I wasn’t briefed — perhaps because Oracle is more scared than its competitors are of hard questions, perhaps for some other reason entirely.*  Anyhow, Oracle Database 11 Release 2 contains an Exadata-only feature called hybrid columnar compression. The Oracle Database 11g Release 2 white paper says “data is grouped, ordered, and stored one column at a time.” But Kevin Closson clarifies:

To read the entire article at its source, please refer to Oracle Exadata hybrid columnar compression