Before starting this exercise, make sure that primary and secondary replicas are accessible to each other and existing AOAG configuration is working fine and in healthy state. You must be connected to the server instance that hosts the primary replica to add a database to availability group.

Add Database to Availability Group using GUI in SSMS

First, we need to configure the corresponding secondary database on each server instance that hosts a secondary replica to save add database wizard processing time. You just need to run the full backup and immediate transaction log backup of the database on primary replica that has been identified to add to the availability group and then restore it to corresponding secondary replica.

Although it is not mandatory step to do it before adding the database to availability group as this can be done during adding database to availability group as well. But it is recommended to prepare your secondary databases on secondary replica before adding it to availability group. Let’s start with configuring secondary replicas followed by adding them to AOAG configuration.

1. First run the full backup and immediate transaction log backup of the database that has been identified to add to the availability group on primary replica.
2. Once backups are completed on primary replica for to-be added database, copy these backups to your secondary replica and restore it with same name in no recovery mode if you want to keep your secondary database inaccessible.
3. Once database will be restored/ synced on secondary replicas, we will start adding this database to existing AOAG configuration using Add Database to Availability Group Wizard on primary replica.
4. Launch SQL Server Management Studio. Connect to the server instance that hosts the primary replica, and expand the server tree.
5. Expand the Always On High Availability folder followed by Availability Groups.
6. Right-click the availability group name, and select one of the following commands:
   • To launch the Add Database to Availability Group Wizard, select the Add Database.
   • To add one or more databases by specifying them in the Availability Group Properties dialog box, select the Properties.
7. Once you click on Add Database… option to add database to existing AOAG configuration, an Introduction wizard will appear that will very similar to the one you might have seen during creating AOAG on your SQL Server Instance.
8. Next screen will come to select databases to proceed with adding them in to AOAG configuration.
9. Third window will come to select initial data synchronization option. Here you should be careful as if you have already configured secondary databases as we did in step 1 and step 2 then you need to select second option that is “Join Only”. If you haven’t configured your secondary database you can go with either first option that will backup the primary database and restore it to secondary replica during this processing only or third option in which you can configure secondary database later. If your database is big in size it will take lot much time to complete the processing.
10. Follow rest of all windows by clicking at next button and once you will click at finish button on last window, your database will be added to existing availability group. You can see the status of this newly added database in to dashboard report or in SSMS.

Add a Database to Availability Group using T-SQL

As I have described n above section, first thing is to configure secondary database so we need to configure the corresponding secondary database on each server instance that hosts a secondary replica to save add database processing time. You just need to run the full backup and immediate transaction log backup of the database on primary replica that has been identified to add to the availability group and then restore it to corresponding secondary replica. Once restore will be completed then follow below steps to add this database to availability group.

1. 1. Connect to the server instance that hosts the server instance that hosts the primary replica.
   2. Use the ALTER AVAILABILITY GROUP statement, as follows:

--AG_name is the name of the availability group.
--database_name is the name of a database to be added to the group.
ALTER AVAILABILITY GROUP AG_name ADD DATABASE database_name

The following example adds the Techyaz database to the AG_Techyaz availability group.

-- Connect to the server instance that hosts the primary replica.
-- Add an existing database to the availability group.
ALTER AVAILABILITY GROUP AG_Techyaz ADD DATABASE Techyaz;
GO

3. If you haven’t configured your secondary database then you need to configure it on each server instance that hosts a secondary replica after adding database to an availability group. If you already added it then you are done with adding your database to existing AOAG configuration. Validate it by launching dashboard report or looking in to SSMS.

I hope you like this article. Please follow our Facebook page and Twitter handle to get latest updates.

Read More:

• How to Remove a Database from AOAG configuration?
• Fix AOAG Listener Issue: Error 19471 The handle is Invalid
• Secondary Replica Showing in Resolving State after AOAG Automatic Failover
• Understanding Backups in Alwayson Availability Group

The post How to Add a New Database to Always On Availability Group? appeared first on Techyaz.com.

• What would be Disk and Performance Impact if we rebuild indexes using ONLINE option?

Resumable Online Index Rebuild

This feature allows us to pause index rebuild operation during its execution at any point and resume it later from the point it was paused. You can use this feature in case you get any higher priority tasks or your server is running out of disk space or facing any performance issue. In addition, this feature rebuilds indexes using only a small amount of log space.

This feature allows us to resume an index rebuild operation after an index rebuild failure, such as after a database failover or after running out of disk space. We can also pause an ongoing index rebuild operation and resume it later. Resumable Online Index Rebuild allows us to rebuild large indexes without using a lot of log space.

Read More

• SQL Server Interview Questions & Answers on Indexes
• What should be Best Value for fill factor in SQL Server?
• How to Avoid Page Split in SQL Server?

Points to Consider

Below are the points you must keep in mind if you are choosing resumable online index rebuild operation.

1. When an index operation is paused, both the original index and the the newly created one require disk space and need to be updated during DML operations.
2. Enables truncation of transaction logs during an index rebuild operation (this operation cannot be performed for a regular online index operation).
3. Resumable Online Index Rebuild feature can be used only with Online Index Rebuild operation. You cannot use it for offline index rebuild operation.
4. We cannot rebuild an index that is disabled.
5. We cannot use ALL option to rebuild existing indexes.
6. Resumable Index Rebuild operation cannot be used to rebuild an existing index that has either computed column or timestamp column as part of the index key.
7. We cannot use SORT_IN_TEMPDB=ON option if we choose to use resumable index rebuild option.

How to use Resumable Online Index Rebuild?

I have given multiple examples to demonstrate the different use cases of resumable online index rebuild operation in this section. If we want to use the resumable index rebuild functionality, we need to execute the online index rebuild with RESUMABLE keyword because Resumable index rebuild supports only during online index rebuild, so we must specify ONLINE = ON along with RESUMABLE = ON option. You cannot use this feature until you mention RESUMABLE = ON in your code because RESUMABLE=OFF is the default value. Run below command to rebuild index online as resumable option.

ALTER INDEX INDEX_Name on Table_Name
REBUILD WITH (ONLINE=ON, RESUMABLE=ON) ;

We can also specify MAXDOP settings during online index rebuild as resumable option to use parallelism. Execute an online index rebuild as resumable operation with MAXDOP=1 by running below command.

ALTER INDEX INDEX_Name on Table_Name 
REBUILD WITH (ONLINE=ON, MAXDOP=1, RESUMABLE=ON) ;

We can also control execution or processing time of resumable online index rebuild by specifying MAX_DURATION option. It specifies the number of minutes that the resumable online index operation will be executed, before being paused. Execute an online index rebuild as resumable operation with MAX_DURATION set to 30 minutes.

ALTER INDEX INDEX_Name on Table_Name 
REBUILD WITH (ONLINE=ON, RESUMABLE=ON, MAX_DURATION=30) ;

Next, we will discuss about pausing these index rebuild operations that are running as resumable option in next section.

Pause Online Index Rebuild running with Resumable Option

If you want to manually pause a running resumable online index rebuild then you just need to use PAUSE clause in above ALTER INDEX statements. Run below command to pause a resumable index rebuild operation.

ALTER INDEX INDEX_Name on Table_Name PAUSE ;

Now we will discuss about how to resume a paused online index rebuild operation in next section.

Resume an Online Index Rebuild running with Resumable Option

As I have mentioned above, you can pause online index rebuild due to any reason. Let’s say suppose you pause it because it is taking lot of time to complete and consuming lot of system resources then you can either resume it later when system has enough resource to run this operation or you can resume it specifying a new value for MAXDOP setting that will allow this operation to use parallelism to finish this task.

Suppose you want to resume an online index rebuild for an index rebuild that was executed as resumable operation specifying a new value for MAXDOP set to 8.

ALTER INDEX INDEX_Name on Table_Name 
RESUME WITH (MAXDOP=8) ;

If you want to resume an online index rebuild for an index rebuild that was executed as resumable operation with the same values then you can remove the MAXDOP options from above command and execute the simple command given below.

ALTER INDEX INDEX_Name on Table_Name RESUME;

You can also resume an online index rebuild operation for an index rebuild that was executed as resumable with different parameters like you can set MAXDOP to 2, set the execution time for the index being running as resumable to 60 minutes and in case of an index being blocked on the lock wait 10 minutes and after that kill all blockers. Run below command to rebuild your indexes with above criteria.

ALTER INDEX INDEX_Name on Table_Name
RESUME WITH (MAXDOP=2, MAX_DURATION= 60 MINUTES,
WAIT_AT_LOW_PRIORITY (MAX_DURATION=10, ABORT_AFTER_WAIT=BLOCKERS)) ;

You can test it in your lower life cycle with multiple options and keywords to get in depth knowledge about this feature.

Abort a Resumable Index Rebuild operation

We can also abort resumable index rebuild operation which is running or paused by executing below T-SQL statement.

ALTER INDEX INDEX_Name on Table_Name ABORT ;

Once you will run above command, your index rebuild operation will be aborted.

Monitor Resumable Index Rebuild Operation

Microsoft has given a system view sys.index_resumable_operations that monitors and checks the current execution status for resumable Index rebuild. You can also get the progress details in percentage of resumable index rebuild operation using this system view.

There is a column named state in this system view that will let us know the state of the resumable index rebuild operation whether it is paused or still running. You can query this system view to see all the resumable index rebuild operations that are currently paused or running.

Run below command to list all resumable index rebuild operations that are in the PAUSE state. State column value zero means online index rebuild is running and value 1 means they are paused. You can also check the percent completion of all resumable index rebuild operations from column PERCENT_COMPLETE from the output received by below command.

SELECT * FROM  sys.index_resumable_operations WHERE STATE = 1;

Related Articles

• Performing Online Index Rebuild Operation
• Understanding SQL Server Indexes and difference between Clustered and Nonclustered Indexes
• Difference between Index Rebuild and Index Reorganize Operation

I hope you like this article. Please follow our Facebook page and Twitter handle to get latest updates.

The post How to Use Resumable Online Index Rebuild Operation in SQL Server? appeared first on Techyaz.com.

Read More on SQL Server Installation on Linux Servers

• Installing SQL Server 2017 on Ubuntu Server
• How to Install SQL Server on Redhat Linux without Internet – Offline Installation
• How to Install SQL Server on Ubuntu without Internet access – Offline Installation
• Installing SQL Tools on RedHat Linux Server

Uninstall SQL Server 2017 on RHEL

Uninstalling SQL Server 2017 that is running on Linux server is totally different process as compared to its windows based SQL Server. Follow below step by step process to uninstall SQL Server 2017 from your RHEL Linux server.

1- Connect to your RHEL server where SQL Server 2017 is running and that needs to be uninstalled from the server. Check whether SQL Server is installed on this machine or not by checking SQL Server service. You can see SQL Server is running on this server.

#Run below command to check SQL Server Service.
systemctl status mssql-server

2- Check SQL Server files along with the database files before removing SQL Server. We will validate SQL Server removal by checking these files post uninstallation.

#Check SQL Server binaries & database files
sudo ls -lrt /var/opt/mssql
sudo ls -lrt /var/opt/mssql/data

Note: Make sure to run full backup of all your databases and keep them in a safer place for future needs.

3- Now, we will uninstall SQL Server by running below command.

#Remove SQL Server from your Linux machine
sudo yum remove mssql-server

You can see details of SQL Server packages that are going to be removed from this machine. These packages are SQL Server and SQL Server Agent that are going to be removed here. Above command will ask us to type y to proceed with the uninstallation and type N to quit this uninstallation. Type y to proceed with the SQL Server removal.

You can see SQL Server and SQL Server Agent both packages have been removed from this machine.

4- Now, remove all SQL Server binaries and database files from its installed location that we checked in second screenshot by running below command.

#Remove database files and SQL binaries.
sudo rm -rf /var/opt/mssql

Here, your SQL Server has been removed from this linux machine. You can check SQL Server binaries and database files by running below commands. We can see no files in these locations because they have been removed now.

#Check database files.
sudo ls -lrt /var/opt/mssql/data

#Check SQL Server files & folders.
sudo ls -lrt /var/opt/mssql

5- Now you can check SQL Server service again by executing below command.

#Check SQL Server Service post SQL Server Removal.
systemctl status mssql-server 

We can see SQL Server is not loaded this time but service is showing as active.

When you will try to restart this service, it will throw you an error that unit not found as shown in below image.

6- Now we need to reboot the server to update SQL Server service status on RHEL. I restarted this linux machine and again checked the SQL Server service. You can see this time it says service could not found.

I hope you like this article. Please follow our facebook page and Twitter handle to get latest updates.

The post How to Uninstall SQL Server 2017 from RedHat Linux Server appeared first on Techyaz.com.

SQL Server 2017 New Features in Database Engine

Let’s discuss SQL Server 2017 features. Below is the list of SQL Server 2017 new features introduced in database engine services.

SQL Server on Linux

SQL Server is not only Windows based RDBMS anymore now you can run it on different flavor of Linux operating systems.  Now you can develop applications with SQL Server on Linux, Windows, Ubuntu, or Docker and deploy them as well on these platforms. SQL Server can now compete more directly with other RDBMS like Oracle which are more popular on Linux. We can say that SQL Server on Linux is one of the most popular SQL Server 2017 features. You can read below articles if you want to install SQL Server on Linux based operating systems.

• 21 Missing Features in SQL Server on Linux
• Install SQL Server 2017 on Redhat Linux – Offline Installation
• Install SQL Server 2017 on Redhat Linux – Online Installation
• How to install SQL Server on Ubuntu – Offline Installation
• How to install SQL Server on Ubuntu – Online Installation

Adaptive Query Processing

SQL Server 2017 introduce a new generation of query processing improvements that will adapt optimization strategies to your application workload’s runtime conditions. During optimization, the cardinality estimation process is responsible for estimating the number of rows processed at each step in an execution plan. When estimates are inaccurate, the query optimizer may make poor decisions regarding algorithm selection and order of operations. This is also one of the most awaited SQL 2017 new features.

Prior to SQL Server 2017, if we make poor assumptions due to bad cardinality estimates, we do not change our query plan execution strategy during execution. Read attached article Adaptive Query Processing to learn more about it.

Resumable Online Index Rebuild

Resumable Online Index Rebuild is another SQL 2017 feature. Now we can pause and resume online index rebuild operation. This feature will be very helpful. Resumable Online Index Rebuild allows you to resume an online index rebuild operation from where it stopped after a failure. For example, you might need to temporarily free up systems resources in order to execute a high priority task or complete the index rebuild in another maintenance window if the available maintenance windows is too short for a large table. Read attached articles to understand in depth information about this feature.

• How to Use Resumable Online Index Rebuild in SQL Server?
• Performing Online Index Operations

Automatic Database Tuning

Automatic tuning is a database feature that provides insight into potential query performance problems, recommend solutions, and automatically fix identified problems. Automatic tuning in SQL Server, notifies you whenever a potential performance issue is detected, and lets you apply corrective actions, or lets the Database Engine automatically fix performance problems.

Graph Database Capabilities

SQL Server offers graph database capabilities to model many-to-many relationships. The graph relationships are integrated into Transact-SQL and receive the benefits of using SQL Server as the foundational database management system.

A graph database is a collection of nodes (or vertices) and edges (or relationships). A node represents an entity (for example, a person or an organization) and an edge represents a relationship between the two nodes that it connects (for example, likes or friends). Both nodes and edges may have properties associated with them.

Cluster less Availability Groups

Now we can configure AOAG\Alwayson Availability group without windows cluster in SQL Server 2017. This feature is added because of another new feature that is to configure AOAG between windows and Linux based SQL Servers. Now you don’t need a windows cluster in place if you want to configure AOAG between windows and Linux based SQL Servers.

Cross-OS AOAG

Availability Groups can now work across Windows-Linux to enable cross-OS migrations and testing. Now we can configure AOAG between windows based SQL Server and Linux based SQL Server. That is why, Microsoft has also given an option for clusterless AOAG.

New Functions

There are few new T-SQL functions added to SQL Server 2017. Below is the list of those new functions. You can click on hyperlinks to get more about them. These functions are very useful for SQL developers.

• CONCAT_WS
• TRANSLATE
• TRIM
• STRING_AGG

New DMVs

There are many new DMVs have been introduced as SQL 2017 new features. Below is the list of such DMVs that have been introduced in SQL Server 2017. You can click on hyperlinks to get more about them.

• sys.dm_tran_version_store_space_usage – Introduced to track version store usage per database.
• sys.dm_db_stats_histogram (Transact-SQL) is added for examining statistics.
• sys.dm_exec_query_statistics_xml
• sys.dm_os_host_info is added to provide operating system information for both Windows and Linux.
• sys.dm_os_sys_info has three new columns added: socket_count, cores_per_socket, numa_node_count.
• A new column modified_extent_page_count, is introduced in sys.dm_db_file_space_usage to track differential changes in each database file of the database.

New DMFs

Below is the list of new DMFs introduced in SQL Server 2017. You can click on hyperlinks to get more about them. 

• This DMF sys.dm_db_log_info is introduced to expose the VLF information similar to DBCC LOGINFO to monitor, alert, and avert potential transaction log issues caused due to number of VLFs, VLF size or shrinkfile issues experienced by customers.
• Another DMF sys.dm_db_log_stats, is introduced to expose summary level attributes and information on transaction log files. This is very useful for monitoring the health of the transaction log.

Here, i have explained about SQL Server 2017 new features. I hope you like this article. Please follow us on our facebook page and on Twitter handle to get latest updates.

The post 10 New Features in SQL Server 2017 Database Engine appeared first on Techyaz.com.