Always On Availability Groups

Rajendra Gupta
Availability group validations

Applying Transaction Logs to the Secondary Replica in SQL Server Always On Availability Groups

July 12, 2019 by

Introduction

SQL Server Always On Availability Groups provides HADR solutions for the SQL databases. Here HA refers to high availability and DR refers to disaster recovery. The priority of this feature is to keep the database highly available and then provide Disaster recovery. Due to this reason, if the secondary replica goes down in a synchronous data commit mode, SQL Server changes commit mode to Asynchronous so that users can continue run the transactions and a secondary replica can be in sync later once it bought up. SQL Listener also points to the primary replica and continues redirects connection to the primary replica.

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Rajendra Gupta
Execution plan and statistics

SQL Server Statistics in Always On Availability Groups

May 27, 2019 by

Introduction to SQL Server Statistics

SQL Server Statistics are an essential part of query performance in SQL Server. They help the query optimizer to prepare a query plan using the distribution of values in participating rows. If we do not have updated statistics, it might lead to resource intensive query execution plan. For example, for a large table having a billion records, SQL may choose to have an index scan instead of an index seek.

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Rajendra Gupta
sql server always on

SQL Server Always On Availability Group Data Resynchronization

May 9, 2019 by

In my previous article Data Synchronization in SQL Server Always On Availability Group, we described a scenario where if a secondary replica goes down in synchronous data commit mode, SQL Server Always on Availability group changes to asynchronous data commit mode. It ensures that users can get their transaction commit irrespective of waiting for a secondary replica to come online.

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Ahmad Yaseen
SQL Server Always on Failover Cluster topography

SQL Server Transaction Log and High Availability Solutions

March 21, 2019 by

In the previous article of this series on the SQL Server transaction log, we discuss the SQL Server database recovery models, Full, Simple and Bulk-Logged, and the how the recovery model option of the database affects the way the SQL Server Engine works with the transaction logs. In this article, we will discuss the different types of high availability and disaster recovery solutions and the role of the SQL Server transaction log in these technologies.

Sreekanth Bandarla
Add Roles and Features Wizard - Remote access

Simulating a Multi Subnet cluster for setting up SQL Server Always On Availability Groups – lab setup

March 14, 2019 by

In this article, we are going to see how to create a multi subnet cluster spanning across multiple subnets for lab purposes. Creating such an environment should help creating Availability groups simulating a far replica residing in a different Data Center (Subnet) acting as a disaster recovery site in your lab for learning/experimenting real world scenarios.

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Ahmad Yaseen

What’s new in SQL Server Management Studio 17.4; Always On AG dashboard enhancements and more

December 27, 2017 by

As all other database engines that require a GUI too to interact with, Microsoft built SQL Server Management Studio as a tool that provides an environment to manage, configure, monitor and administrate the SQL Server infrastructure for different kind of instances, that are installed locally at your machine, on a remote server with Windows or Linux operating systems or hosted in the cloud such as SQL Azure or Azure Data warehouse.

Recall that the SQL Server Management Studio consists of the Object Explorer, which is used to view and manage all objects within the SQL Server instance, the Template Explorer, that is used to deal with the scripting text files and the Solution Explorer, that is responsible for building the projects that contain list of T-SQL scripts in SQL Server.

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Derik Hammer

Synchronizing SQL Server Instance Objects in an Availability Group

September 8, 2017 by

Availability groups can no longer be considered new. The feature was released in SQL Server 2012 but I often notice that SQL Server Failover Cluster Instances (FCIs) are much better understood. For a very long time, when people thought about SQL Server they thought about the entire instance as a unit. Microsoft has been implementing new features and services which begin to segment the concept of an instance from the concept of a database.

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Prashanth Jayaram

How to Configure TDE database with AlwaysOn using the Azure Key Vault in SQL 2016

July 28, 2017 by

One of the recent tasks I undertook on configuring Transparent Data encryption (TDE) using asymmetric key protection with Azure Key Vault with Always On opened a different dimension on securing data for me. Even though it seems slightly complex, if you have the key details, the steps are in fact, really straight forward.

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Ahmad Yaseen

How to add a TDE encrypted user database to an Always On Availability Group

April 27, 2017 by

SQL Server Transparent Data Encryption, also known as TDE, is a “data at rest” encryption mechanism that is introduced in SQL Server 2008 as an Enterprise Edition feature. TDE is used to perform a real-time I/O encryption for the SQL Server database data, log, backup and snapshot physical files, rather than encrypting the data itself, using either Advanced Encryption Standard (AES) or Triple DES (3DES) encryption.

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Ahmad Yaseen

How to Configure Read-Only Routing for an Availability Group in SQL Server 2016

March 23, 2017 by

The SQL Server Always On Availability Groups concept was introduced the first time in SQL Server 2012 as an enterprise-level high availability and disaster recovery solution that will replace the database mirroring feature. Always On Availability Group provides a high availability solution on the group level, where each group can contain any number of databases that can be replicated to multiple secondary servers known as Replicas.

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Ahmad Yaseen

SQL Server 2016 Always On Availability Group with Direct Seeding

January 12, 2017 by

SQL Server Always On Availability Groups are an enterprise-level high-availability and disaster-recovery feature introduced the first time in SQL Server 2012as an alternative to database mirroring. A set of user databases that fail over together forms the availability group. These availability databases are hosted by the availability replicas and can be readable- writable at the primary replica and up to eight sets of secondary replica databases that can be configured to be read-only databases. The availability groups fail over due to the availability replica’s level issues and not the ones caused due to database level issues such as data loss or database corruption.

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Derik Hammer

Measuring Availability Group synchronization lag

August 9, 2016 by

With all of the high-availability (HA) and disaster recovery (DR) features, the database administrator must understand how much data loss and downtime is possible under the worst case scenarios. Data loss affects your ability to meet recovery point objectives (RPO) and downtime affects your recovery time objectives (RTO). When using Availability Groups (AGs), your RTO and RPO rely upon the replication of transaction log records between at least two replicas to be extremely fast. The worse the performance, the more potential data loss will occur and the longer it can take for a failed over database to come back online.

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Murilo Miranda

Understanding backups on AlwaysOn Availability Groups – Part 1

November 30, 2015 by

Since the AlwaysOn Availabiliy Groups feature was introduced, we got new options to make the backups strategy more complete, but also more complex. Taking an advantage of secondary replicas, we can offload both, the FULL and even the Transaction Log backups from the Primary Replica to the Secondary, leaving the Primary replica dedicated to serve the production application.

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