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Production Database Administration

[Video] Can You Tell When a Rollback Will Finish?

Last Updated April 11, 2020

I happened to see this DBA.StackExchange.com question about killing a big delete, and I really felt for the admin involved: Four days ago a user ran the command below on a table with 400,000,000 rows. It’s still running and the log file is increasing in size. Hoo boy. When you kill a query, it’s hard…

[Video] How Can I Measure If My Database Does More Reads Than Writes?

Last Updated April 5, 2020

Brent Ozar

Production Database Administration, Videos

When someone asks you, “Is this database read-intensive or write-intensive?” you probably look at sys.dm_io_virtual_file_stats to measure the file activity – but that isn’t really correct. After all, your users run a lot of queries all day that are simply satisfied from the buffer pool. SQL Server caches your data so it doesn’t have to hit…

That's it, I'm rolling back to SQL Server 6.5

Breaking News: SQL Server 2019 CU2 Breaks Agent.

Last Updated March 4, 2020

Brent Ozar

Breaking News, SQL Server 2019

That’s it, I’m rolling back to SQL Server 6.5 You reported it here in the comments, and over at SQLServerUpdates, and in this DBA.StackExchange.com question. The official word is in: yep, SQL Server 2019 Cumulative Update 2 breaks Agent jobs on some servers, causing them not to run. That official word is only in that…

Which SQL Server Enterprise Edition Should I Download?

Last Updated February 6, 2020

Brent Ozar

Production Database Administration

When you’re downloading SQL Server, it’s important to choose Enterprise Core, not Enterprise. The plain “Enterprise” one is limited to just 20 CPU cores. But let’s say you didn’t know that, and you waltzed over to the download page. There are two Enterprises listed, and it’s not really clear what the differences are between the two:…

Why Database Monitoring Tools Are So Hard to Interpret

Last Updated January 27, 2020

Brent Ozar

Monitoring

SentryOne’s Greg Gonzalez recently published a post about “Why Wait Stats Alone Are Not Enough.” Sure, Greg’s obviously biased towards his own monitoring tool, but his post is really well-written and fair. I want to explain the same story, but from a different (and simplified) angle. Say we’ve got a really simple database server, and…

Three Reasons to (Temporarily) Change Max Worker Threads

Last Updated January 7, 2020

Brent Ozar

Configuration Settings

When you go to the deli, there’s a “take a number” dispenser where you tear off a number and wait for your number to be called. If you walked into a deli and you saw 50 people lined up all waiting their turn, and you went to take a number and the dispenser was completely…

Microsoft’s Guidance on How to Set MAXDOP Has Changed

Last Updated December 16, 2019

Brent Ozar

Production Database Administration

For years, SQL Server’s Maximum Degree of Parallelism (MAXDOP) – the number of cores that a parallel query could use – defaulted to 0, meaning unlimited. This led to rampant CXPACKET waits because queries went wild with parallelism. Overly wild, like me after six shots of tequila within an hour wild. (It’s not my fault:…

DBA Training Plan 23: Congratulations! Now, It’s Your Turn.

Last Updated September 21, 2019

Brent Ozar

DBA Training Plan, Professional Development

I bet you think you suck at databases. You’re sitting there on your computer, reading all kinds of blogs, watching presentations online, and you’re thinking, “Everybody knows more about databases than I do.” We all feel that way. There’s even a name for it: Impostor Syndrome. I have it too. For example, about a decade…

DBA Training Plan 22: Where to Learn More

Last Updated September 15, 2019

Brent Ozar

DBA Training Plan, Professional Development

Whew. We’ve worked through a couple dozen posts together in this DBA Training Plan, and you’re still just getting warmed up. First, pick your specialty. Here’s some of the more popular specializations in the SQL Server business: Production administration – managing uptime, building new boxes, troubleshooting clusters, setting up storage, designing virtualization infrastructures Performance tuning…

DBA Training Plan 21: Building a New SQL Server

Last Updated September 18, 2019

Brent Ozar

DBA Training Plan, High Availability

I have a secret setup checklist. Oh sure, our free First Responder Kit has a SQL Server setup checklist that walks you through a few things you need to do before you install, plus a few things to do immediately afterwards. That’s good. It’s actually pretty darned good. But it’s not the secret checklist. Gather round and cover your…

DBA Training Plan 20: Planning Your Next Server

Last Updated September 9, 2019

Brent Ozar

Architecture, DBA Training Plan

When the business decides it’s time to give up fixing the old server because it’s not fast enough or reliable enough, stop. The worst thing you can do is jump directly to the hardware vendor’s site, check a few boxes, and order a new shiny server that ends up with exactly the same problems as…

DBA Training Plan 19: The L-Word, Licensing

Last Updated September 6, 2019

Brent Ozar

DBA Training Plan, Licensing

You’ve gotten through a lot of this training. You’ve tried fixing the problem with indexes, query tuning, and judicious application of various configuration switches. You’ve been watching webcasts and using free scripts, but… Things just aren’t getting better. Before you start browsing your cloud vendor’s sizing price list or your favorite server vendor’s build-and-price site,…

Mitch Bottell is preparing to take an exclusive lock on some BBQ.

DBA Training Plan 18: Managing Concurrency

Last Updated September 3, 2019

Brent Ozar

DBA Training Plan, Locking, Blocking, and Isolation Levels

Locking isn’t a problem – queries are gonna lock data. As long as nobody else wants the lock, you can take your sweet time locking it, and it won’t show up as a problem. (That’s one of the many reasons queries work so well in development, and then hit performance issues in production.) Blocking, now…

DBA Training Plan 17: Should You Partition Your Tables?

Last Updated September 2, 2019

Brent Ozar

DBA Training Plan, Partitioning

In the last episode, I talked about knowing when it’s time to scale out: identifying when our data is getting to be so large that we have to split it across multiple servers, and I explained why that is so challenging. But what about table partitioning – SQL Server’s ability to break up a single…

I would like to scale out my Porsche collection.

DBA Training Plan 16: Is It Time to Scale Out?

Last Updated August 27, 2019

Brent Ozar

Architecture, DBA Training Plan

In our last episode, we found out what your server was waiting on. In the closing remarks, I mentioned that you should find out which queries are causing the problem, and focus your mitigation efforts there. You might have circled back to the episode where we covered sp_BlitzCache, used a @SortOrder parameter that lines up…

DBA Training Plan 15: What’s Your SQL Server Waiting On?

Last Updated August 30, 2019

Brent Ozar

DBA Training Plan, Wait Stats

You’re here, dear reader, because you weren’t “classically trained” as a database administrator. You didn’t graduate from the University of Sciencing Computerses with a Master’s of Transactional Processing. You probably got your start as a developer or sysadmin, and gradually fumbled your way here. You’re used to monitoring stuff from the OUTSIDE using things like…

DBA Training Plan 14: POP QUIZ!

Last Updated August 28, 2019

Brent Ozar

DBA Training Plan

AH-HA! You didn’t know there would be one of these, did you, hotshot? You’ve been reading along in the series, just smiling and nodding, pretending you’re keeping up, but not really doing the homework. BUSTED! Put your books away and get your pencils out. Backup & Recovery Questions: How many production SQL Servers do you…

DBA Training Plan 13: Why Do Cached Plans Go Bad?

Last Updated September 5, 2019

Brent Ozar

DBA Training Plan, Execution Plans

It’s a little bit of a trick question: what could make a good query plan turn bad? In the last episode, we used sp_BlitzCache to spot the most resource-intensive, longest-running query plans in your server’s cache. Go run those queries again, right now, and I bet you’re going to see plans in the cache that…

DBA Training Plan 12: What Query Plans Are In Cache?

Last Updated August 11, 2019

Brent Ozar

DBA Training Plan, Execution Plans, sp_BlitzCache

In the last episode, while talking about the basics of executing queries, I said that SQL Server caches execution plans in memory, reusing them whenever the same query gets executed again. I’ve also talked about the dynamic management views (DMVs) that let you query what’s in SQL Server’s memory. Let’s put those two things together…

DBA Training Plan 11: The Basics of Executing a Query

Last Updated August 15, 2019

Brent Ozar

DBA Training Plan, Execution Plans

Up til now in the DBA Training Plan, we’ve been taking inventory of our servers, making sure the data’s well-protected, and understanding the basics of how the data’s stored in indexes inside those data files. Now, let’s start looking at performance, and let’s start by zooming really far out to think about how SQL Server…