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Clustering_factor
Cost Based Oracle – Fundamentals (November 2005) But the most interesting function for our purposes is sys_op_countchg(). Judging from its name, this function is probably counting changes, and the...
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Hakan Factor
Here’s a quick and dirty script to create a procedure (in the SYS schema – so be careful) to check the Hakan Factor for an object. If you’re not familiar with the Hakan Factor, it’s the value that gets...
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ISS
I’d like to dedicate this posting to fellow Oak Table member Richard Foote, for reasons that the readers we have in common will immediately recognise: http://www.youtube.com/watch?v=KaOC9danxNo The...
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Parse Time
Dominic Brooks published a note recently about some very nasty SQL – originally thinking that it was displaying a run-time problem due to the extreme number of copies of the lnnvl() function the...
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Webinars
Reminder: The webinars on “Smarter Statistics in 11g” are on tomorrow (Friday) at 2:00 pm and 6:00 pm. There’s a waiting list for the 6:00 pm event, so if you’ve signed up but can’t make it please...
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Performance Monitoring
Updated – just a quick reminder for next week; I’ll be doing a short webinar next Wednesday comparing the performance monitoring tools Oracle and SQL server provide. I think I may have broken my record...
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UKOUG
The call for papers is open for Tech 13 – the “server-side” conference of the UKOUG. The conference was getting so big that we’ve split Apps from Server Tech and will be running the two conferences...
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gather_plan_statistics – 2
Some time ago – actually a few years ago – I wrote a note about the hint /*+ gather_plan_statistics */ making some informal comments about the implementation and relevant hidden parameters. I’ve...
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Dynamic Sampling – 2
I’ve written about dynamic sampling in the past, but here’s a little wrinkle that’s easy to miss. How do you get the optimizer to work out the correct cardinality for a query like (the table creation...
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CUR Gets
Here’s an interesting anomaly from the OTN database forum – PL/SQL track. It’s a single row delete from a table that does a huge number of db block gets and (in the first example shown) physical reads....
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How to hint
Here’s a live example demonstrating a point I’ve often made – you have to be very detailed in your hinting or Oracle will find a way to obey your hints and do the wrong thing. A recent posting on the...
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French Philosophy
From Mohamed Houri, here’s a French translation of all my “Philosophy” notes to date.
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ROWID
Here’s a suggestion to help you avoid wasting time. If you ever include the rowid in a query – not that that should happen very commonly – make sure you give it an alias, especially if you’re using...
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Parallel DML
Parallel DML is not enabled by default, and it’s easy to forget this and think you’ve made an operation “as parallel as possible” by declaring objects parallel or putting in hints for parallelism. A...
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Delphix
If you’ve been keeping an eye on my Public Appearances page you’ll know that I was scheduled to go on line with Kyle Hailey for a second (more technical) discussion about Delphix and virtual databases...
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12c I/O debug
By my count there are 109 new v$ and gv$ dynamic performance views in 12c (so far) – and Glen Fawcett has posted a short note on a group that may be of particular benefit to anyone who finds they...
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maxthr – 3
In part 1 of this mini-series we looked at the effects of costing a tablescan serially and then parallel when the maxthr and slavethr statistics had not been set. In part 2 we looked at the effect of...
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12c trivia
Weighing in at a massive 54 characters – the longest parameter name in 12c is: _adaptive_scalable_log_writer_disable_worker_threshold Followed very closely by (you guessed it)...
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Tweet
I don’t know why I ever agree to go anywhere near Doug Burns – he usually manages to persuade me into doing things I don’t want to. This time (at a meeting of the London Oracle Beer group) he’s...
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12c Statspack Hack
Starting from a comment on an old statspack/AWR page, with a near-simultaneous thread appearing on OTN, (do read both) here’s a quick summary of getting statspack onto 12c with containers. (For...
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