John McCormack DBA

SQL Server Databases and Cloud

Test read intent connections to an AG Listener

By 4 Comments

To test read intent connections to an AG Listener, I prefer to use SQLCMD but you can also test easily using SSMS.

SQLCMD

The -Kreadonly switch is your key to success here but remember to also specify the database using -d. When not set (and with an initial catalog of master for my login), I found I always got the primary instance back during my check. This simple omission cost me hours of troubleshooting work, because I was convinced my listener wasn’t working correctly. In fact, I just wasn’t testing it correctly.

Read/Write Connections
-sqlcmd -S "SQL01-AG1-list" -d WideWorldImporters -E -q "SELECT @@SERVERNAME;"

Read only Connections
-sqlcmd -S "SQL01-AG1-list" -d WideWorldImporters-E -q "SELECT @@SERVERNAME;" -Kreadonly

The instance that you are connected to will show in the command prompt. Type exit to leave sqlcmd.

SSMS

In object explorer, click Connect and choose Database Engine.

Then, in the bottom right hand side of the dialog box, click on Options >>

In Connection Properties, Click Connect to database and then <Browse server ..>. Choose a DB that is in your availability group.

Connect To Server SSMS

Then click on Additional Connection Parameters and type in ApplicationIntent=ReadOnly

ApplicationIntent=ReadOnly SSMS

Click connect and run SELECT @@SERVERNAMEand you should expect to see the instance name of your secondary replica, providing you have set up the read only routing correctly.

If you change connection and remove ApplicationIntent=ReadOnly from the Additional Connection Parameters, you should see the result as the name of your primary instance.

Summary

Hopefully these 2 simple techniques to test read intent connections to an AG Listener will be useful and help save you time. It’s a simple blog post but I wanted to write it because I was looking at the problem in too much depth and missing the obvious mistake of choosing my database context.

Popular posts

Put tempdb files on D drive in Azure IAAS

By 7 Comments

Data loss warning Azure VMTempdb files on D drive you say?

Azure warn you not to to store data on the D drive in Azure VMs, but following this advice could mean you are missing out on some very fast local storage. It’s good general advice because this local storage is not permanently attached to your instance, meaning you could lose data or log files if your VM is stopped and restarted but what if you could afford to lose certain files? Say files that are recreated during startup anyway.

TempDB is the ideal candidate for this. No other database is suitable! Putting the tempdb data and log files onto D drive can be achieved quite easily with a little bit of effort. And you will most likely see a big improvement in tempdb read/write latency.

Just look at these results! Even for someone like me who sometimes looks at charts and often can’t see the obvious, I don’t think there is any denying when the change took place here.

tempdb latency azure IAAS
Blazing fast now

 

Overview of how to configure SQL Server to use D drive for tempdb on Azure VM

  1. Run the ALTER DATABASE command for all of the files you need to change e.g.
    • ALTER DATABASE [tempdb] MODIFY FILE ( NAME = N'tempdev', FILENAME = 'D:\TempDB\tempdev.mdf')
  2. Create Folder D:\TempDB or something similar
  3. Restart SQL Server and make sure your files are created in D: as expected
  4. Manually remove any old tempdb files still lying around

Now to make sure tempdb is created when the VM restarts

  1. Create a Powershell script which will create the D:\TempDB folder on startup and start the SQL services
  2. Change the startup type of your SQL Services to Automatic (Delayed Start)
  3. Test this thoroughly in dev before you rely on it in production. If it doesn’t work, you’ll need to remember how you configured tempdb and manually create the folders, then start SQL Server. Not a fun task under pressure.
More tempdb goodness

Configuring TempDB for SQL Server 2016 instances

IT Certification Category (English)728x90

Glasgow SQL User Group Presentation – SQL Server on AWS

By Leave a Comment

You can run SQL Server on AWS?

SQL Glasgow User Group Logo

Tonight, I presented my SQL Server on AWS talk to the Glasgow SQL User Group. This blog post was prepared in advance so I’ll add some observations on how I found the experience once I get a chance.

I’ve attached some important links from the talk which provide more detail on the subjects covered.

Links to my AWS content

AWS documentation

For slides or examples, please contact me directly and I’ll share them.

Running SQL Server on RDS SQLBits presentation

By Leave a Comment

Running SQL Server on RDS

I presented on Running SQL Server on RDS at SQLBits. It was  a lightning talk, so only 5 minutes.

You can download my slides from here:

Running SQL Server on RDS

Further interesting links:

My more detailed post on running SQL Server on AWS (RDS vs EC2)

Amazon RDS for SQL Server FAQs

SQL Server Agent Information

Outstanding batch wouldn’t clear on sys.dm_fts_outstanding_batches

By Leave a Comment

Outstanding batch wouldn’t clear on sys.dm_fts_outstanding_batches

I had an issue where an outstanding batch wouldn’t clear on sys.dm_fts_outstanding_batches. This meant the full-text index was not working when queried using the CONTAINSTABLE syntax. I used a series of queries from Glen Allan Berry’s post to help me identify what the problem was with my full-text index.

sys.dm_fts_outstanding_batches

I restarted the Full-Text service with no success. This seemed like the natural thing to do and my colleagues said that it had worked in the past when FTS had stalled. Unfortunately, this didn’t help the situation.

I then rebuilt the Full Text Catalog and still had no success. This took 5 minutes however the rebuild was blocked so would normally have been much quicker.

As the full-text index was built on an indexed view, my next idea was to rebuild the clustered index of the view. To my surprise, this actually solved the problem and I no longer had any outstanding FTS batches. My query using CONTAINSTABLE returned a success and the developers confirmed their application was fixed. In my opinion, this is well worth a try.

sys.dm_fts_outstanding_batches cleared

The point of sharing this post is the hope that it will help someone else with the same issue. It’s not my greatest ever post and I’m not certain why the index rebuild helped but its been a good lesson to me that I need to learn more about Full-Text Indexing for SQL Server. Anything else I learn will be used to add useful information to this blog post.

Any suggestions for good resources in the comments would be highly appreciated as this looks like an area that has been far from extensively covered by other bloggers.