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Understand the Oracle ?proof? Myth

Oracle Tips by Mike Ault

Be Careful In What You Prove

I have recently been researching scuba diving sites within the USA for a possible series of articles for a scuba magazine. Believe it or not, I do have interests outside of Oracle! One of the sites, Rock Lake, Wisconsin is of particular interest for what lies beneath its turgid waters. But if I reveal too much now it might dilute the future article. What it has brought to light is the fact that you must be careful not only in what you believe to be true but in what you prove to be true. The tales of what lay beneath Rock Lake vary from lost Atlantis to only legends. I am sure if the two camps were brought together, bloodshed would ensue as each defended their point of view. To each of the camps, what they believe is the truth.

Many people believe that truth is immutable, that what is true now is always true. However, times change, technology changes, even (especially) theology. It was not so long ago that respected scientists believed that a Doctor washing his hands was not professional, that traveling at speeds in excess of 30 miles per hour would do irreparable damage to the human frame, that traveling faster than the speed of sound would result in a crash much like hitting a brick wall, or that setting off an atomic bomb would ignite the atmosphere and annihilate mankind.

Of course all of the above has been proven incorrect. Now there are those that propose that the cherished notion that the speed of light is absolute is also a myth that will be dispelled with time (believe it or not, the "warp" drive of Star Trek fame has a basis in theoretical physics, of course it requires more energy than we can currently produce, but in medieval times wouldn't all of our current technology give us a one way ticket to the witches bonfire? ) however, as much energy as we can currently produce is perhaps a far cry from as much energy as we can produce. Some go as far as to claim that some super-novas are proof that some technologies lost control of zero-point energy.

So also must we view "proofs" given of things that are acceptable incurrent technology, in Oracle and in other technologies, as only transient in nature? Watch out that the "proofs" of today don't become tomorrows old wives tales.

For example, it wasn't too long ago that separation of indexes and tables in databases was a good and accepted method for improving performance. Of course this was because otherwise they would be on the same disk platter if they weren't separate and would conflict. Now of course with the almost universal implementation of RAID technology (redundant arrays of independent/inexpensive disks) this becomes unneeded (sometimes, depending on the amount of data stored on each disk in the array). It could be demonstrated, when they shared a single disk, that moving indexes away from tables improved performance. Based on that proof, no longer valid, some will say that moving indexes away from tables always improves performance.

Likewise the old saw that moving to RAW devices in UNIX (raw meaning the application was responsible for IO) would result in large improvements in performance. This of course was based on the premise that all of the buffering in the OS for non-raw filesystems caused delays. Now modern file systems can be set to eliminate this buffering and journaling delays and the performance gains from raw have diminished to nearly null. Of course rebuilding the objects within the databases involved, (tables and indexes) restoring them to proper parameters that they may have exceeded through years of neglect also helped.

So now we have a new crop of experts providing proofs (sometimes limited to a single-user, small database on a laptop) that their methods are the best and no doubt their proofs will be sited long after they are useful or meaningful and their expert advice will fade into old DBA tales as new technologies and methods become the rage. This is as it should be.

I guess I am trying to say, in a rambling way, that today sage advice becomes tomorrows old tale. We must all be aware of what the current methods are, realize when the old methods no longer apply, and gracefully accept new ways if we are to grow and prosper. However, we must also recognize when the "proper" method evolves and mutates into a "new" method, leaving the old ways to die away.

So be careful in what you prove and how you prove it. What seems clever today may come back to haunt you. You may be apologizing several years down the road for what is right now, but not in the future. The net is an amazing place. No doubt you can find numerous places where I may have expounded on the virtues of separation of indexes and tables, on rebuilding indexes frequently or other items that have since been proved, for current versions, old DBA tales. I like others before, am not immune to time and neither is my advice.

If any paper you read is older than a year or two, I suggest you take its advice with a big grain of salt as it may be applicable only to history and not current events.

Critics love to dig up old papers, presentations and advice given and use it to bludgeon people into believing they are the only authority. Take this type of advice with a grain of salt as well. In time, their advice will be referenced, out of date and out of style.

If you like Oracle tuning, see the book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.


 

 

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