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Category: Administration

Filtering Stored Procedure Results

Published 2019-08-29 by Kevin Feasel

Thomas Rushton shows how to filter any stored procedure’s result set and uses sp_who as an example:

sp_who – useful – up to a point. Particularly when the server is busy, and you’re looking for something specific (eg to see if certain processes are out of a database before running an update)

If the server is busy – don’t you wish there was a way to run something like

sp_who WHERE dbname = 'foo'

Yeah. Unfortunately, it doesn’t work like that.

That doesn’t work, but Thomas shows you what does.

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CPU Usage DMV in SQL Server on Linux

Published 2019-08-28 by Kevin Feasel

Tejas Shah announces an improvement to sys.dm_os_ring_buffers in SQL Server 2019 RC1 on Linux:

Sys.dm_os_ring_buffers DMV has been a key DMV used for monitoring SQL Server by built-in tools as well as third party monitoring utilities. When SQL Server 2017 was released on Linux, unfortunately this DMV did not return correct CPU usage information by SQL Server process. SQL Server team is glad to announce that the starting with SQL Server 2019 release candidate, the sys.dm_os_ring_buffers DMV returns SQL CPU utilization correctly. This improvement should benefit the SQL Server monitoring ecosystem on Linux by providing a way to monitor SQL Server CPU usage and enable decision making to engage corrective action if required.

This brings it in line with what we have on Windows.

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SQL Server Database Recovery Models

Published 2019-08-27 by Kevin Feasel

John McCormack goes into the three database recovery models available in SQL Server:

This post is about database recovery models for SQL Server databases. Having the correct recovery model for a database is crucial in terms of your backup and restore strategy for the database. It also defines if you need to do maintenance of the transaction log or if you can leave this task to SQL Server. Let’s look at the various recovery models and how they work.

Click through for a description of each, including recommendations of when to choose each.

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Common VM Configuration Issues

Published 2019-08-26 by Kevin Feasel

Erik Darling takes us through some of the most common issues when setting up VMs to run SQL Server:

Everyone’s on VMs these days. That’s cool. Nothing against computers.

But here’s how people screw up SQL Server on VMs bigtime:

– Fewer than 4 cores (this is a licensing minimum)
– Multiple single-core sockets
– Not fully reserving memory
– Oversubscribing hosts

All four of those are bad and Erik explains why.

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Accelerated Database Recovery and Filegroups

Published 2019-08-22 by Kevin Feasel

Randolph West shows a change to Accelerated Database Recovery in SQL Server 2019 CTP 3.2 and later:

ADR makes use of a per-database version store, instead of putting everything in the transaction log and TempDB. In most cases, the payoff more than makes up for valuable transaction log and TempDB storage. In my testing, enabling ADR requires around 10% additional storage in your database file.

The reason for this post, however, is to mention that SQL Server 2019 CTP 3.2 introduced the ability to choose which filegroup you want to use for the version store, which will help with performance.

Read on to see how you enable this.

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Change Tracking in SQL Server

Published 2019-08-12 by Kevin Feasel

Tim Weigel covers the basics of change tracking in SQL Server:

There aren’t a lot of parameters here. You can set change tracking on or off, you can specify your retention period, and you can specify whether to enable auto-cleanup or not.

For the retention period, you have the choice of DAYS, HOURS, or MINUTES. If you don’t specify retention, SQL Server will configure change tracking with a retention period of 2 days. If you provide a number but don’t specify the interval, SQL Server will default to days. The minimum retention period is 1 minute.

This post specifically covers enabling change tracking at the database level.

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Maintaining SSISDB

Published 2019-08-08 by Kevin Feasel

John McCormack was in a jam:

I made 2 unsuccessful attempts at running the SSIS Server Maintenance Job. However, after several hours of processing and still no available free space in the database, I knew the job wasn’t coping with the sheer number of rows it had to delete. The deletes all happen from the parent table (internal.operations) and then all child tables using using cascading deletes. This approach maintains referential integrity but is not great for performance.

Due to this, I needed a new approach to the maintenance of SSISDB. As we hadn’t maintained these tables for 13/14 months, I was asking too much of SQL Server to let me delete everything at once. 

Read on for the solution.

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Snapshot Isolation

Published 2019-08-08 by Kevin Feasel

Gerald Britton takes us through snapshot isolation in SQL Server:

Snapshot isolation avoids most locking and blocking by using row versioning. When data is modified, the committed versions of affected rows are copied to tempdb and given version numbers. This operation is called copy on write and is used for all inserts, updates and deletes using this technique. When another session reads the same data, the committed version of the data as of the time the reading transaction began is returned.

By avoiding most locking, this approach can greatly increase concurrency at a lower cost than transactional isolation. Of course, “There ain’t no such thing as a free lunch!” and snapshot isolation has a hidden cost: increased usage of tempdb.

Gerald covers both varieties, Read Committed Snapshot Isolation and proper Snapshot Isolation. RCSI is definitely worth understanding in almost any environment, and even Snapshot Isolation has its uses.

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Calculating Memory Consumption by Object

Published 2019-08-06 by Kevin Feasel

Max Vernon has a script to help you figure out which objects are consuming the most buffer pool space:

SQL Server caches object data in memory in the buffer pool. Understanding memory consumption by object can be crucial for performance. For instance, you may have a large logging table consuming 90% of the buffer pool. Moving older rows out of the logging table might allow you to reduce memory consumption if you really only care about the last 2 weeks of log records. The script below takes a snapshot of sys.dm_os_buffer_descriptors, then links it to the objects in each database on the instance. The output shows which objects are in memory, along with how much memory is being consumed by each object.

Click through for the script.

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Distributed Transactions on Linux

Published 2019-08-05 by Kevin Feasel

Tejas Shah and crew announce distributed transactions with SQL Server on Linux:

With SQL Server 2017, a new era was heralded with SQL server being available to deploy on Linux (and Linux based container) systems. While all functionality of the SQL Server engine were brought over as is to SQL Server on Linux, some of the functionality which depended on Windows system processes such as distributed transactions (which relies on MSDTC service) were not brought over immediately.

Well, now your wait is over.

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