Roll With It


"I know one thing for certain; it is much harder to tell whether you are lost than whether you were lost,
for, on many occasions, where you are going is exactly where you are. On the other hand, if you often find
that where you've been is not at all where you should have gone, and, since it's much more difficult to
find your way back from someplace you've never left, I suggest you go  (more...)

Parallel Reality


"Expect everything, I always say, and the unexpected never happens."
-- Norton Juster, The Phantom Tollbooth

The following question was recently posted in an Oracle forum:


hi Friends,
I see  this wait event latch: parallel query alloc buffer, when a job meant for doing some cleanup ran this query.
Why does this wait event come happen? , i searched google,MOS no exact hit for explanation of the exact same event.
Looking at query does  (more...)

That’s Not A Latch


"They all looked very much like the residents of any small valley to which you've never been."
-- Norton Juster, The Phantom Tollbooth

While investigating latches another interesting process popped up that’s smaller and lighter, that performs a similar function, called a mutex. So what is a mutex? By definition it’s a mutual exclusion object that locks memory structures to prevent concurrent sessions from changing the same object at the same time, so in (more...)

Latch, What Latch?!?


"I know one thing for certain; it is much harder to tell whether you are lost than whether you were lost, 
for, on many occasions, where you are going is exactly where you are. On the other hand, if you often find
that where you've been is not at all where you should have gone, and, since it's much more difficult to
find your way back from someplace you've never left, I suggest you go  (more...)

Extended Engagement


"You see, to tall men I'm a midget, and to short men I'm a giant; 
 to the skinny ones I'm a fat man, and to the fat ones I'm a thin man."
-- Norton Juster, The Phantom Tollbooth

Oracle offers, in release 12.1.0.2, the option of increasing the maximum string length from the standard 4000 to a whopping 32767; depending on the nls_length_semantics setting this could be in bytes or in (more...)

The BLOB


"Have you ever heard a blindfolded octopus unwrap a cellophane-covered bathtub?"
-- Norton Juster, The Phantom Tollbooth

An interesting question was posted on the Oracle General Database forums fairly recently, inquiring about creating a B-Tree index on a BLOB column to speed queries looking for NULLs in that BLOB. The conventional wisdom states that, because it’s a BLOB, NULLs shouldn’t be present. And because it’s a BLOB, containing binary data, creating sucn an index (more...)

Adjusting Things


"The only thing you can do easily is be wrong, and that's hardly worth the effort." 
-- Norton Juster, The Phantom Tollbooth

Query tuning is both an art and a science and, because of this, usually occurs on a case-by-case basis. There may be occasions, though, where a series of queries, similar in structure and differing in predicate values, need to be tuned. Rather than go through each and every query, setting up a (more...)

You Bet Your ASCII


"Why, did you know that if a beaver two feet long with a tail a foot and a half long can build a dam twelve 
feet high and six feet wide in two days, all you would need to build Boulder Dam is a beaver sixty-eight
feet long with a fifty-one-foot tail?"
"Where would you find a beaver that big?" grumbled the Humbug as his pencil point snapped.
"I'm sure I don't know,"  (more...)

GrACE Period

The time is fast approaching where it will be three years since I was graced with the status of Oracle ACE, and I’ve enjoyed every minute of it. I can’tspeak highly enough of the program and its steadily growing list of members. But don’t think for a minute that once someone becomes an Oracle ACE or Oracle ACE Director the work stops; nothing could be further from the truth.

Sharing my knowledge got me here (more...)

You’re A Natural


"'Why is it,' he said quietly, 'that quite often even the things which are correct just don't seem to be right?'"
-- Norton Juster, The Phantom Tollbooth

A YouTube video is currently being promoted in the database community regarding joins, including the variety of joins available in most database engines (the engine referred to in the video is Oracle). A very good discussion ensues covering inner, left outer, right outer, full outer and cross (more...)