September 24, 2012 at 9:50 am
Hi all:
I recently turned on a trace flag on our production server to send information to the error log when a deadlocks occurs. So, now, I'm getting my feet wet with investigating the occasional deadlock. I'm looking at one today where one process was doing a SELECT and another process was doing an UPDATE. I'm reading up for background information in my SQL 2005 70-431 study guide which says that,
"a deadlock always requires at least two processes, and each of those processes must be making a modification to data."
Intuitively, that makes sense. However, in the deadlock information I am looking at right now in the error log, one of the processes appears to only be doing a SELECT, which is confusing. The other is an UPDATE within stored procedure, which I understand. These are the only two SQL Statements I'm seeing in the group of records in the error log that are related to the deadlock. So, what am I not understanding correctly?
September 24, 2012 at 10:19 am
The study guide is incorrect. Not only are reader-writer deadlocks possible, they're actually very common forms of deadlocks
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
September 24, 2012 at 10:26 am
I see. Thanks for the information. I've heard the 2005 study guide was better than the 2008 one, but evidently it has errors as well.
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