John Watson's blog
Submitted by John Watson on Sun, 2015-02-08 07:48
Excellent exposition of a very effective SQL tuning metodology
Submitted by John Watson on Sun, 2015-01-18 08:59
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.
Submitted by John Watson on Sun, 2014-08-31 10:17
How much undo and redo does Oracle generate for different operations? More than you might think.
Submitted by John Watson on Sat, 2014-07-19 10:39
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.
Submitted by John Watson on Sun, 2014-07-06 06:02
Concurrent inserts into a table will often result in crippling buffer busy wait problems as sessions serialize on access to the last block(s) of the table segment. Using hash clusters can remove the issue.
Submitted by John Watson on Sun, 2014-06-08 11:55
Many people are terrified of global indexes, one reason being that partition DDLs on the table will either render them unusable, or take forever as they are updated. Deferred global index maintenance solves this, and should be an important driver for the 12c upgrade.
Submitted by John Watson on Wed, 2014-06-04 19:56
Why use interpreted PL/SQL when native compiled PL/SQL is so much faster? No reason at all - except that interpreted is the default, and most DBAs never change this. They should.
Submitted by John Watson on Sun, 2014-05-11 06:16
Can this parameter really boost performance? This simple test suggests that it can.
Submitted by John Watson on Sat, 2014-05-10 06:28
Unified Audit is a major architectural change: fast, easy, and impossible for the DBA to bypass. On upgrade to Oracle 12c, you really should enable it. The earlier method that we all use is pretty awful.
Submitted by John Watson on Mon, 2014-04-07 09:02
The concept of an adaptive plan is that execution of a statement can start with one plan, and (during execution) switch to another. A pretty amazing capability. No need to run the statement to completion and try again: correct it in flight.