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Category: DBCC

DBCC CLONEDATABASE and Production Deployments

Published 2024-03-28 by Kevin Feasel

Madhumita Tripathy takes a step back:

DBCC CLONEDATABASE command generates a schema-only copy of a database. Effective March 1, 2025, Microsoft will discontinue support for the use of the DBCC CLONEDATABASE command as a tool to copy database to production environment. The command is intended for diagnostic and troubleshooting purposes only. Any use of the command for purposes other than those specified will not be supported by Microsoft from the aforementioned date. All editions of Microsoft SQL Server 2016 and later versions are affected by this change.

Now I’m a bit curious about the why behind this post.

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Breaking out a CHECKDB Run

Published 2024-02-14 by Kevin Feasel

Mikey Bronowski fixed a problem:

Regular execution of DBCC CHECKDB is a cornerstone practice for DBAs, ensuring that databases are free from corruption. However, this routine maintenance can sometimes feel more like a Herculean task, especially when DBCC CHECKDB runs slower than a snail in molasses, or worse, gets terminated because it runs too slow.

Read on to see what Mikey did to fix the issue. This is a good reminder that sometimes, there is no single silver bullet, but a whole magazine of lead can still get you to the same location.

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Table Results for DBCC PAGE

Published 2023-12-22 by Kevin Feasel

Andy Yun is pleased:

Am playing around with Always Encrypted for the first time. I was just following along the basic tutorial and encrypted some columns in my AutoDealershipDemo database. But then I decided to go crack open the data page using my friend DBCC PAGE.

Read on to see how you can get the results of DBCC PAGE into a table. My recollection is that there are some limits to what it can write into the table, but it’s pretty good on the whole.

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Triggering Dumps for Specific Errors and States

Published 2022-09-29 by Kevin Feasel

Bob Dorr has a plan:

I had an inquiry about dbcc dumptrigger today and realized that state filtering was added to dbcc dumptrigger but not well known.

You can collect a process dump (SQL Dumper) when a specific error occurs using XEvent (error_reported/ex_raise2 events with dump capture action) or dbcc dumptrigger.

The common use of dbcc dumptrigger is: dbcc dumptrigger(‘set’, 208) to produce a dump when error 208 is encountered.

This is pretty useful, especially if you’re troubleshooting a bug in the database engine.

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When DBCC_OBJECT_METADATA becomes a Bottleneck

Published 2021-07-28 by Kevin Feasel

Paul Randal takes us through another latch:

Continuing my series of articles on latches, this time I’m going to discuss the DBCC_OBJECT_METADATA latch and show how it can be a major bottleneck for consistency checks prior to SQL Server 2016 under certain circumstances. The issue affects DBCC CHECKDB, DBCC CHECKTABLE, and DBCC CHECKFILEGROUP, but for clarity I’ll just reference DBCC CHECKDB for the rest of this post.

You might wonder why I’m writing about an issue that affects older versions, but there are still a huge number of SQL Server 2014 and older instances out there, so it’s a valid topic for my series.

Read on to understand what DBCC_OBJECT_METADATA does and how it can become a bottleneck on those older versions of SQL Server.

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CHECKDB: Repairing with Data Loss

Published 2021-06-08 by Kevin Feasel

Chad Callihan explains what that CHECKDB option which should sound really scary means:

Just because REPAIR_ALLOW_DATA_LOSS might get your database up and running quickly doesn’t make it a good option. It could wrongly be considered a shortcut or an easy button to get handle corruption. Some may run REPAIR_ALLOW_DATA_LOSS, see their database back online, and call it a day. Let’s look at why some things are too good to be true.

Read the whole thing.

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Offloading Maintenance Operations

Published 2021-04-21 by Kevin Feasel

Taryn Pratt has a process for offloading maintenance operations onto another server:

Early on when I started working on the SQL Servers at Stack Overflow, we were taking daily backups. We had a handful of databases that were being restored for other processes, but the majority weren’t actively tested to ensure the backups were good. Since you never want to be in a situation where you need to restore a database and find it doesn’t work, my goal was to create a process to automatically restore our backups to a separate server, and then run DBCC CHECKDB on it.

This is a T-SQL-driven process and I appreciate that. If you want a Powershell-driven process, Kevin Hill has you covered.

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DBCC CHECKDB on Large Databases

Published 2020-11-06 by Kevin Feasel

Aaron Bertrand shares some thoughts on CHECKDB:

We have a lot of data. Some of that data is stored in large databases (dozens of terabytes each). In some shops, this is an excuse to not run integrity checks. We are not one of those shops.

But we don’t run full CHECKDB operations in production; we have a set of servers dedicated to testing our restores and running checks. We follow a lot of the guidance in these articles:

– CHECKDB From Every Angle: Consistency Checking Options for a VLDB

– Minimizing the impact of DBCC CHECKDB : DOs and DON’Ts

– Minimize performance impact of SQL Server DBCC CHECKDB

Read the whole thing, even if you aren’t dealing with 30+ TB databases.

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Building an Azure Function to Automate CHECKDB

Published 2020-09-11 by Kevin Feasel

Arun Sirpal shows us how to build an Azure Function:

The title is a mouthful and so is this post. In the past I have linked to blog posts from Microsoft that say consistency checks for Azure SQL Database is the responsibility of Microsoft. (https://azure.microsoft.com/en-gb/blog/data-integrity-in-azure-sql-database/)

However, Paul Randal got me thinking about his thoughts on it (via his insider email). Forming the core of this post. If you desire to run DBCC CHECKDB against Azure SQL Database (which I know people do) – how can you do this? There are many ways, but for this blog post – Enter Azure functions. There are many moving parts to this, but once setup and coded it is a very satisfying experience. Let’s dig in. I am NOT going to copy and paste every little element of the high-level guide from Microsoft, there is no point in that but I will show you the links that you need to setup the relevant function app project then the tailored bits around CHECKDB forms the bulk of this post.

This isn’t necessary to do, but if you want to learn how Azure Functions work, it’s a good example of working through the mechanics.

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