John Watson's blog
Standard Edition release 126.96.36.199 is now available. Download it from the usual locations. But along with the great news, comes some news that is not so great: the licensing model has changed.
Following previous blog re BASIC compression, here are a couple of simple tests with Advanced Compression - which is supposed to survive conventional DML.
BASIC table compression is bundled with all database editions, and can achieve respectable compression ratios. But beware! Subsequent DML may be disastrous.
The ability to quiesce the database was introduced in release 9, but to this day I find that many people are not aware of it. It can be really useful - so let's describe it. I'll begin by positioning the quiesce capability: when is it useful. Then detail how to do it, then reverse engineer the mechanism.
Excellent book - I've just posted this review on Amazon:
Another example of what I think of as "the self-tuning database". Setting optimizer_dynamic_sampling=11 can fix many performance problems, without the DBA needing to use his brain at all.
Excellent exposition of a very effective SQL tuning metodology
Following a question on OTN https://community.oracle.com/message/12801175 I did another test on redo and undo, just to prove that frequent COMMIT can be bad for performance. The results surprised me. I expected that row-by-row commit would be worse then a single commit at the end of a multi-row transaction, but I hadn't expected it to be this bad. As well as being much slower, both undo and redo volumes are vastly greater.
How much undo and redo does Oracle generate for different operations? More than you might think.
Buffer busy wait and related events can cripple performance of concurrent inserts. Bad in a single instance database, far worse in a RAC (think "gc buffer busy"). Often the problem is because of a primary key populated from a sequence. Reversing the index can fix this problem.