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Deferrable RI – 2
A question came up on Oracle-L recently about possible locking anomalies with deferrable referential integrity constraints. An update by primary key is taking a long time; the update sets several...
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Lock Time
Here’s a little detail I was forced to re-learn yesterday; it’s one of those things where it’s easy to say “yes, obviously” AFTER you’ve had it explained so I’m going to start by posing it as a...
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Deadlocks
A recent question on the OTN forum asked about narrowing down the cause of deadlocks, and this prompted me to set up a little example. Here’s a deadlock graph of a not-quite-standard type: Deadlock...
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Flashback Logging
One of the waits that is specific to ASSM (automatic segment space management) is the “enq: FB – contention” wait. You find that the “FB” enqueue has the following description and wait information when...
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RI Locks
RI = Referential Integrity: also known informally as parent/child integrity, and primary (or unique) key/foreign key checking. I’m on a bit of a roll with things that I must have explained dozens or...
View ArticleLock Types
Every now and again I have to check what a particular lock (or enqueue) type is for and what the associated parameter values represent. This often means I have to think about the names of a couple of...
View ArticleDML Tablescans
This note is a follow-up to a recent comment a blog note about Row Migration: So I wonder what is the difference between the two, parallel dml and serial dml with parallel scan, which makes them behave...
View ArticleIndex ITL Limit
Here’s a little script that I wrote more than 10 years ago when investigating some undesirable behaviour with indexes. I’ve just rediscovered it after seeing it mentioned in a comment to an old...
View ArticleORA-00054 pt.1
If you don’t recognise the number the relevant extract from the oraus.msg file is: 00054, 00000, "resource busy and acquire with NOWAIT specified or timeout expired" // *Cause: Interested resource is...
View ArticleORA-00054 pt.2
This is the follow-up to an initial post that covered some details of using the errorstack and ksq traces as and aid to finding the cause of an intermittent ORA-00054: resource busy and acquire with...
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