Clik here to view.
Deadlock
Here’s a deadlock graph the appeared on Oracle-L and OTN a couple of days ago. Deadlock graph: ---------Blocker(s)-------- ---------Waiter(s)--------- Resource Name process session holds waits process...
View ArticleClik here to view.
Row Lock Waits
Here’s one I keep forgetting – and spending 15 minutes trying to think of the answer before getting to the “deja vu” point again. I’ve finally decided that I’ve got to write the answer down because...
View ArticleClik here to view.
Deadlock Detection
By some strange coincidence, the “London Bus” effect perhaps, there have been three posts on the OTN database forum in the last couple of days relating to deadlocks; and they have prompted me to...
View ArticleClik here to view.
Lock Bug
Here’s an oddity that I ran into a little while ago while trying to prepare a sample trace file showing a particular locking pattern; it was something that I’d done before, but trace files can change...
View ArticleClik here to view.
Deadlocks
Here’s a deadlock graph that might cause a little confusion: Deadlock graph: ---------Blocker(s)-------- ---------Waiter(s)--------- Resource Name process session holds waits process session holds...
View ArticleClik here to view.
v$lock
The problem of slow queries on v$lock just came up again on the OTN database forum, so I thought I’d better push out a post that’s been hanging around on my blog for the last few months. This is...
View ArticleClik here to view.
Shrink Space
Here’s a lovely effect looking at v$lock (on 11.2.0.4) select sid, type, id1, id2, lmode, request, ctime, block from V$lock where sid in ( select sid from V$session where username = 'TEST_USER' ) order...
View ArticleClik here to view.
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...
View ArticleClik here to view.
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...
View ArticleClik here to view.
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...
View ArticleClik here to view.
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...
View ArticleClik here to view.
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...
View Article