Press "Enter" to skip to content

Category: Replication

Replication In Azure SQL DB Managed Instances

Published 2018-03-19 by Kevin Feasel

Tara Kizer looks at transactional replication in Azure SQL Database Managed Instances:

I have a love-hate relationship with replication. Mostly hate due to latency and errors, but it does serve its purpose. Before Availability Groups came out, I used Transactional Replication to copy data from the production OLTP database to another server so that we could offload reports.

Will it work with a Managed Instance?

My relationship is closer to hate-hate-love-hate-hate-love-hate.  Tara also provides some good advice about watching replication latency stats.

Comments closed

Replication Update: Dynamic Parameter Loading

Published 2018-02-27 by Kevin Feasel

Sourabh Agarwal announces a new feature with SQL Server replication:

When a new agent user profile is created and assigned to an agent, relevant entries are added to the [dbo].[MSagent_profiles] and the [dbo].[MSagent_parameters] tables in the MSDB database on the Distributor server. The values in the tables are updated whenever a parameter value is updated for the Profile. These values are reloaded from the tables, whenever a replication agent is restarted. As part of the improvement a new profile parameter “ProfileReloadInterval” with a default value of 300 seconds, was added to the profiles. This parameter dictates the interval at which the agent reloads the values from the tables. If using the default value, the agent will try and reload the values from the MSDB tables every 5 minutes. If it encounters that any of the above-mentioned parameter values have changed, the new values will be used by the agents.

I don’t work with replication enough to really see the benefit, but I’m sure somebody is giddy about this.

Comments closed

Tracking Replication Throughput

Published 2017-10-19 by Kevin Feasel

Phil Grayson has a couple of replication-related queries:

It’s a right laugh when replication goes wrong, if you haven’t been there and use replication heavily, you’re in for the night / early morning of your life. Like any issue, the cause of replication problems could be one of many, but checking what commands are being passed through the distributor is always worthwhile, as an inefficient query could be updating the same data over and over, putting unnecessary strain on the distributor, infrastructure or the subscribers.

Read on for those queries.

Comments closed

Transactional Replication And SQL On Linux

Published 2017-09-22 by Kevin Feasel

Phil Grayson shows a way to get transactional replication working on Linux:

Microsoft have stated that transactional replication isn’t supported on Linux and we’re not sure if they intend to in the future. This means that if you try to add the server to a publisher, you get the following message. So you can’t use the GUI and it also means that you can’t use pull as the necessary files won’t be there.

Despite that warning, there is a way to set up a push subscription; click through for that way.

2 Comments

Important Stored Procedures For Transactional Replication

Published 2017-07-31 by Kevin Feasel

Drew Furgiuele (who always starts off with the red ring) explains three important replication stored procedures:

We all have that one scenario where replication caused us some major headaches. It’s through these headaches, though, that the search for better ways to handle problems comes up. Through my time with replication, I’ve researched and used a lot of system tables, views, and stored procedures to diagnose or fix replication problems. There’s actually a lot of things you can get into if you’re so inclined. If you put me on the spot though, and asked me “Drew, what do you think are the most helpful replication internal objects to know?” I’d tell you I have three, and they’re all stored procedures.

Here then, in no particular order, are three system stored procedures that I feel any DBA that has to deal with transactional replication should at least be aware of. They each have a unique purpose, and each can be used to quickly monitor, fix, or even destroy replication forcibly, respectively.

Read the whole thing.

Comments closed

Transactional Replication And Temporal Tables

Published 2017-06-13 by Kevin Feasel

Transactional replication found Drew Furgiuele’s little black book of T-SQL syntax and went ballistic when it found out Drew was seeing temporal tables on the side:

So let’s say you ran this script (or, maybe someone checked it in as a database change to production). For a while, things are great: you’re making changes to data on your publisher and things are flowing nicely to your subscribers. Sooner or later though, someone’s going to ask you to set up a new subscription (or maybe you need to reinitialize one). Let’s simulate that on my lab: we’re going to remove Person.Address from replication and we’re going to put it back, and then create a snapshot. The key difference here is that now, Person.Address has system versioning turned on. When we try and add the table back to the publication, we’re in for a shock:

This could come back to bite you, so if you use replication and are interested in temporal tables, read this closely.

Comments closed

Transactional Replication Procedures

Published 2017-04-12 by Kevin Feasel

Drew Furgiuele offers up warnings when thinking about rolling your own transactional replication stored procedures:

In the above picture, we can see that it did replicate the execute statement, and that it affected 19,972 rows on the replica, and it only took 67ms! Sounds awesome, doesn’t it? Here’s a way to handle large batch updates at your publishers without overwhelming your replication setup. But before you go changing everything, you should probably understand that this has some really, really bad side effects if you’re not careful. Let’s look at three really big ones.

All in all, it’s a fairly risky move but might be worth the performance improvements.

Comments closed

Replication And TDE

Published 2017-03-16 by Kevin Feasel

Drew Furgiuele looks at how replication interacts with Transparent Data Encryption:

But what happens if we set up a transactional replication publication on this database and do a snapshot? Remember that when you create a publication, your distributor and subscriber(s) need to know which network share (or FTP server) to drop all the data and schema definitions to so they can be read in by the distribution agent and recreated. In my example, I’m dropping them to a network share. Once the snapshot completes, let’s go check out our subscriber database…

Uh oh. The same query returned zero results at the subscriber. Which means no encryption! Replication won’t replicate encryption, at all. So if you have a requirement to encrypt your data at the source, you’ll need to do it on your subscribers too.

Drew points out a couple important gotchas which might lead to you exposing information you didn’t intend to make available.

Comments closed

Replication Extended Events

Published 2017-03-09 by Kevin Feasel

Drew Furgiuele goes hunting for the most dangerous creature of all, replication-related extended events:

Extended events are great; they have all the goodness of profiler except you don’t use profiler. Win/win! More to the point, extended events let you quickly and easily view, sort, and aggregate events that occur on your instances. They also have powerful filters (really, a “where” clause) to limit noise. You have way more control over what you monitor, how you store the data, and how you view and use it. This makes them perfect use to track replicated transactions, since we want to measure at both an individual level and the aggregate.

I fired up management studio and went to “New Session” looking for some replication event goodness and I found…

… nothing. I tried looking for events that had even parts of the name replication in it. No such thing, apparently.

This doesn’t deter Drew and he ends up building some interesting events to infer the correct answers.

Comments closed

Replication With SQL_Variant Datatypes

Published 2017-03-01 by Kevin Feasel

Kevin Eckart ran into an interesting issue when trying to set up transactional replication on a table with a sql_variant datatype:

I recently tasked with setting up Transactional Replication in SQL 2008 R2. While this in and of itself isn’t necessarily complicated, I did run into an issue that kept the initial snapshot from being created. One of the articles (tables) in the publication had two columns that were defined with a SQL_Variant type and the snapshot agent could not convert those columns to create the snapshot. I tried the various column convert settings in the article properties, but they did not help.

Read on for the answer.

Comments closed