New class: Immersion Event on Azure SQL Database, Azure VMs, and Azure Managed Instance

Tim’s been working closely with the development team on Azure Managed Instance, presented with them at Ignite recently, and has been presenting internally at Microsoft field offices to their clients, as well as working with our own clients extensively on Azure and Azure migrations. With all this Azure experience, and by popular demand, Tim’s updated his two-day IEAzure class and expanded it to four days!

It’s now IEAzure: Immersion Event on Azure SQL Database, Azure VMs, and Azure Managed Instance and it’ll debut in May 2019 in Chicago, as part of our usual set of Spring classes. Note: there’s a US$200 discount for registering before the end of 2018!

The modules are as follows:

  • Azure Virtual Machines
  • Migrating to Azure Virtual Machines
  • Azure SQL Database
  • Migrating to Azure SQL Database
  • Azure Managed Instance
  • Azure Security
  • Administration and Scheduling
  • Additional Azure Features

You can read a more detailed curriculum here and all the class registration and logistical details are here.

We hope to see you there!

Calling all user group leaders! We want to present for you in 2019!

By the end of December, we at SQLskills will have presented remotely (and a few in-person) to more than 100 user groups and PASS virtual chapters around the world in 2018!

We’d love to present remotely for your user group in 2019, anywhere in the world, as long as the time/timezone works reasonably. It’s not feasible for us to travel to user groups or SQL Saturdays unless we’re already in that particular city, but remote presentations are easy to do and are becoming more and more popular. We haven’t had any bandwidth problems doing remote presentations in 2018 to groups as far away as Australia and India, plus Israel, Canada, Ireland, UK, Slovakia, and Poland. This way we can spread the community love around user groups everywhere that we wouldn’t usually get to in person.

Note: we have our own Webex accounts which we generally use, or we can use your GoToMeeting or Webex, but you must use computer audio – we won’t call in by phone as the sound quality is too poor. We also will not use Skype/Lync as we’ve had too many problems with it around user group laptops and sound.

So, calling all user group leaders! If you’d like one of us (me, Kimberly, Jon, Erin, Glenn, Tim) to present remotely for you in 2019 (or maybe even multiple times), send me an email and be sure to include:

  • Details of which user group you represent (and if sending from a shared user group account, your name)
  • The usual day of the month, meeting time, and timezone of the user group
  • Which months you have available, starting in January 2019 (a list of available dates would be ideal)
  • Whether you’d like just one or multiple

And I’ll let you know who’s available with what topics so you can pick. We have around 20 topics across the team that we can present on.

What’s the catch? There is no catch. We’re just continuing our community involvement next year and we all love presenting :-)

There’s no deadline for this – send me an email at any time and we’ll see what we can do.

We’re really looking forward to engaging with you all!

Cheers

PS By all means pass the word on to any SharePoint and .Net user group leaders you know too.

Lazy log truncation or why VLFs might stay at status 2 after log clearing

 Earlier this year I was sent an interesting question about why the person was seeing lots of VLFs in the log with status = 2 (which means ‘active’) after clearing (also known as ‘truncating’) the log and log_reuse_wait_desc showed NOTHING.

I did some digging around and all I could find was an old blog post from 2013 that shows the behavior and mentions that this happens with mirroring and Availability Groups. I hadn’t heard of this behavior before but I guessed at the reason, and confirmed with the SQL Server team.

When an AG secondary is going to be added, at that point in time, the maximum LSN (the Log Sequence Number of the most recent log record) present in the restored copy of the database that will be the secondary must be part of the ‘active’ log on the AG primary (i.e. that LSN must be in a VLF on the primary that has status = 2). If that’s not the case, you need to restore another log backup on what will be the new secondary, and try the AG joining process again. Repeat until it works. You can see how for a very busy system, generating lots of log records and with frequent log backups (which clear the log on the primary), catching up the secondary enough to allow it to join the AG might be difficult, or necessitate temporarily stopping log backups on the primary (possibly opening up a window for increased data loss in a disaster).

To make this whole process easier, when a database is an AG primary, when log clearing occurs, the VLFs don’t go to status = 0; they remain ‘active’ with status = 2. So how does this help? Well, the fact that lots more VLFs are ‘active’ on the AG primary means that it’s more likely that the maximum LSN of a new secondary is still part of the ‘active’ log on the primary, and the AG-joining succeeds without having to repeat the restore-retry-the-join over and over.

(Note: the log manager knows that these VLFs are really ‘fake active’ and can reuse them as if they were ‘inactive’ if the log wraps around (see this post for an explanation) so there’s no interruption to regular operations on the AG primary.)

It’s a clever little mechanism that someone thought of to make a DBA’s life a bit easier and AGs less problematic to set up.

And now you know – log clearing won’t *always* set VLF statuses to zero.