VLFs: How Many Are Too Many?

Randolph West looks at a baseline for the maximum number of Virtual Log Files for a database:

In a transaction log with too many or too few VLFs we might experience performance issues under a normal workload, as well as during the backup and restore process.

So what is the “right” amount? In customer engagements, I follow a guideline proposed by Glenn Berry of SQLskills.com in his Diagnostic Information Queries, to keep the number of VLFs at or below 200. In my opinion, any number higher than that is cause for concern.

On the other hand, Brent Ozar Unlimited has a popular script called sp_Blitz which proposes a maximum VLF count of 1000. To Brent, a number higher than that is cause for concern.

I tend toward the lower number, but if you have a smoothly-functioning environment and some databases have 700 or 900 VLFs, I probably wouldn’t give it a second thought.

dbachecks Improvements

Rob Sewell shows off some improvements in the dbachecks library:

With the latest release of dbachecks we have added a new check for testing that foreign keys and constraints are trusted thanks to Cláudio Silva b | t

To get the latest release you will need to run

You should do this regularly as we release new improvements frequently.

We have also added better descriptions for the checks which was suggested by the same person who inspired the previous improvement I blogged about here

Click through for more details.

Installing OpenSSH Server: Windows 10 Edition

Anthony Nocentino shows us how to install OpenSSH server on Windows 10 update 1803:

So in yesterday’s post we learned that the OpenSSH client is included with the Windows 10, Update 1803!  Guess, what else is included in this server, an OpenSSH Server! Yes, that’s right…you can now run an OpenSSH server on your Windows 10 system and get a remote terminal! So in this post, let’s check out what we need to do to get OpenSSH Server up and running.

First, we’ll need to ensure we update the system to Windows 10, Update 1803. Do that using your normal update mechanisms.

With that installed, let’s check out the new Windows Capabilities (Features) available in this Update, we can use PowerShell to search through them.

Anthony goes through the steps for configuration, so check that out.

Updating A Table Using Change Data Capture Without Downtime

Robert Blackburn takes us through the steps of updating a table which uses Change Data Capture without taking a downtime window:

Steps

  1. Stop jobs that process CDC (SSIS).

  2. Inside a transaction with isolation level serializable: Alter Table schema and create temporary CDC table

  3. Copy old CDC rows to new table excluding dup rows (based on [__$seqval])

  4. Disable old (original) CDC table (schema is outdated). Will drop table

Click through for the rest of the steps and an example script.

RDP Error: CredSSP Encryption Oracle Remediation

Kerry Tyler explains an error message popping up in RDP sessions:

In March, a vulnerability in CredSSP (Credential Security Support Provider) was patched, which would affect authentication via RDP (this is outlined in advisory CVE-2018-0886).  However, it was implemented in such a way that the behavior change didn’t have to be “honored” by either the server or the client involved in an RDP session.

The intent was that this would be controlled by GPO in enterprise environments, and a new GPO setting to activate or deactivate this behavior was released at the same time.

GPO settings have a default value, which they will use when nothing has been explicitly set for a particular setting. In this case, the GPO has three possible values: Force Updated Clients (for servers to only take connections from patched clients), Mitigated (for both, and on a workstation means that it won’t fall back to old/insecure behavior when attaching to unpatched servers), and Vulnerable (for both, and means what it sounds like–anything goes!).

In March, the default behavior was set to “Vulnerable”, which means everything kept working for everyone. But in the May security rollup, the default setting for that GPO was flipped to “Mitigated” if there was not an explicit setting for it…

If you get this error, the best thing is to patch the machines involved, but Kerry shows the workaround you can use if you need to use RDP in the meantime to connect to an unpatched machine.

OpenSSH Now Built Into Windows

Anthony Nocentino is excited about the latest release of Windows 10:

Today is a big day! The OpenSSH client version 7.6p1 is now part of the Windows 10 operating system! Microsoft released Windows 10 Update 1803 and included in that release is the OpenSSH client, which is installed as part of the update.

That’s right an SSH client as part of the Windows operating system by default! Also included with this update is the OpenSSH Server which is included as an Windows Feature on Demand.

Let’s take a look at what this is all made of!

I’m still going to use PuTTY for my SSH needs, but it’s nice to see that there’s a default option if you’re in a pinch and working on an unfamiliar server.

Config Options For Checks In DBAChecks

Rob Sewell explains a new features in dbachecks:

You can see the name, the current value and the description

Ah thats cool he said so

How Do I Know Which Configuration Is For Which Check?

Well, you just…. , you know…… AHHHHHHH

Rob then made this possible.  Click through to see how you can determine which configuration works for which checks.

Creating Azure SQL Database Managed Instances Via ARM Templates

Jovan Popovic shows how us how to build a Managed Instance of Azure SQL Database using Powershell and an ARM template:

Values that you need to change in this request are:

  • name – name of your Azure SQL Managed Instance (don’t include domain).

  • properties/administratorLogin – SQL login that will be used to connect to the instance.

  • properties/subnetId – Azure identifier of the subnet where Azure SQL Managed Instance should be placed. Make sure that you properlyconfigure network for Azure SQL Managed Instance

  • location – one of the valid location for Azure data centers, for example: “westcentralus”

  • sku/name: GP_Gen4 or GP_Gen5

  • properties/vCores: Number of cores that should be assigned to your instance. Values can be 8, 16, or 24 if you select GP_Gen4 sku name, or 8, 16, 24, 32, or 40 if you select GP_Gen5.

  • properties/storageSizeInGB: Maximum storage space for your instance. It should be multiple of 32GB.

  • properties/licenceType: Choose BasePrice if you don’t have SQL Server on-premises licence that you want to use, or LicenceIncluded if you can have discount for your on-premises licence.

  • tags(optional) – optionally put some key:value pairs that you would use to categorize instance.

Click through for the template and a quick Powershell script which shows how to use the template.

Useful Azure SQL Database T-SQL Statements

Arun Sirpal has a few T-SQL statements to help manage an Azure SQL Database database:

Creating a database

Very easy to create something like the below – a S2 database.

CREATE DATABASE [MeeTwoDB]
( MAXSIZE = 5GB, EDITION = 'standard', SERVICE_OBJECTIVE = 'S2' ) ;
--checking details
SELECT Edition = DATABASEPROPERTYEX('MeeTwoDB', 'Edition'), ServiceObjective = DATABASEPROPERTYEX('MeeTwoDB', 'ServiceObjective')

Read on for several more examples.

Troubleshooting SQL Server Error 18456 State 73

Thomas Rushton reproduces an error state in SQL Server:

A question asked on one of the forums today wasn’t easily answerable by Googling. Summary of the question “I have error 18456 State 73 – why?

Google seemed remarkably quiet on the subject of that particular state code. Even Aaron Bertrand’s list of causes of state codes for SQL Server error 18456 missed this one.

However, some searching did find a link to what appears to be some in-depth VMWare VSAN training documentation that includes that error in some logging information, which made me wonder if it was related to the error 18456 state 38 that followed.

Read on for more details.

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