TechNet Magazine: July 2011 SQL Q&A column
The July edition of TechNet Magazine is available on the web now and has the latest installment of my regular SQL Q&A column. This month's topics are: Deferred log truncation from concurrent data...
View ArticleInitial VLF sequence numbers and default log file size
We're teaching on-site with a financial client in New York for two weeks and in a session this morning on log file architecture I was asked why the VLF (virtual log file) sequence numbers in a new...
View ArticleTechNet Magazine: September 2011 SQL Q&A column
The September edition of TechNet Magazine is available on the web now and has the latest installment of my regular SQL Q&A column. This month's topics are: Online index operations logging changes...
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Understanding data vs log usage for spills in tempdb
Earlier this morning I noticed a discussion on the SQL MCM distribution list (that all the original MCM instructors are part of) that was trying to make sense of a huge disparity between tempdb data...
View ArticleUsing fn_dblog, fn_dump_dblog, and restoring with STOPBEFOREMARK to an LSN
I've blogged a bunch about using the undocumented fn_dblog function I helped write (and I've got a lot more to come :-) but here's one I haven't mentioned on my blog before: fn_dump_dblog (although I...
View ArticleSurvey: transaction log files per database (code to run)
In this survey I'd like to see what the distribution of the number of log files per database is for your servers. I'm planning to do similar surveys through the rest of the year around data files and...
View ArticleMultiple log files and why they’re bad
About a month ago I kicked off a survey with some code to run to figure out how many log files your databases have (see here). There are all kinds of misconceptions about transaction logs and how to...
View ArticleParent transaction ID in 2012 fn_dblog output
All kinds of little bits of information have been added to the output of various DMVs, functions, and commands in SQL Server 2012. One which I only discovered recently, and about which I’m really...
View ArticleNew 7.5 hour online course on logging, recovery, and the transaction log
As you know we're recording a lot of content for Pluralsight, and they've just published my latest course today: SQL Server: Logging, Recovery, and the Transaction Log. This is a carefully structured,...
View ArticleTracking page splits using the transaction log
Whenever I’m teaching about index fragmentation I get asked how to track page splits proactively. This can be useful to discover fragmentation occurring in indexes you didn’t know had fragmentation...
View ArticleThe Accidental DBA (Day 30 of 30): Troubleshooting: Transaction Log Growth
This month the SQLskills team is presenting a series of blog posts aimed at helping Accidental DBAs ‘keep the SQL Server lights on’. It’s a little taster to let you know what we’ll be covering in our...
View ArticleHow to tell who changed a log file characteristic?
My good friend Orson Weston (@weston12) posted a question to #sqlhelp on Twitter earlier: Is there a way out of the box to find when and who changed the max file size for a log file? You can’t tell...
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Are I/O latencies killing your performance?
In this post I explain some methods for investigating and reducing high tempdb and transaction log I/O latencies that can severely hamper the performance of your workload. Back at the end of August I...
View ArticleMore on using Transaction SID from the transaction log
Back in 2012 I blogged about using fn_dblog and fn_dump_dblog to figure out the point at which something occurred that you’d like to restore to just before (e.g. a table drop). I also mentioned that...
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What is the most worrying cause of log growth (log_reuse_wait_desc)?
Two weeks ago I kicked off a survey that presented a scenario and asked you to vote for the log_reuse_wait_desc value you’d be most worried to see on a critical database with a 24×7 workload. Here are...
View ArticleWhen is fast recovery used?
It’s been a bit light on technical posts here over the last few months but now that summer’s over I’ll be ramping up again with lots of cool stuff planned. First up is a question that came up on the...
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Delayed Durability in SQL Server 2014
One of the cool new features in SQL Server 2014 is delayed durability (available in all Editions), which is described in detail in Books Online here. I think I’m going to see a lot of people turn this...
View ArticleImportant change to VLF creation algorithm in SQL Server 2014
Since SQL server 2014 was released back in April last year, there have been some rumblings about changes to how many VLFs are created when the log is grown or auto-grown (I’ll just say auto-grown from...
View ArticleIncomplete checkpoints and recovery
Back in 2009 I blogged about how checkpoints work (see How do checkpoints work and what gets logged) and I received a question in email on Monday that I thought would make a good little blog post. The...
View ArticleREPLICATION preventing log reuse but no replication configured
Last week, for the second time in as many weeks, I was sent a question in email from someone who had a transaction log that was growing out of control. He’d already queried log_reuse_wait_desc for the...
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