I've been looking at the Oracle doc concerning index-organized tables. It looks like they offer great advantages : less disk space, great perf for DML and selects using the primary key (they say so in the doc, but I also did some tests which were positively surprising), as well as great availability (since secondary indexes are still available during maintenance operations) at almost no cost. So my (double) question is : are there major drawbacks not stated in the doc, and is this type of table available in the standard version of Oracle, or only in the Enterprise version ?
Another drawback is that one cannot create a DOMAIN index (Oracle Text) on an IOT.
Apart from these drawbacks, IOT can be very interesting : in tests I've done, they perform 4 times better than normal tables for inserts, and 3 times better for updates on a field part of the PK (tests on insert/update of 150000 records on a 11,5 million rows table, in the same conditions). Other updates as well as selects using the PK index also showed better results, while the overhead when using a secondary index doesn't seem to be that important (for now, I'd say max 10%, if any).