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DBAs most often face scenarios where they need to capture graphical execution plan of a query currently running on a live production instance because of multiple reasons like:

  • why a particular SPID is causing blocking
  • why is my query running slow
  • why isn’t the index getting used
  • which operator is costing more and why

While there are multiple ways to retrieve the execution plan, below is the query I always keep handy as I can run this safely on a live production server with minimal effort.

SELECT CONVERT(XML, c.query_plan) AS ExecutionPlan
FROM sys.dm_exec_requests a with (nolock)
OUTER APPLY sys.dm_exec_sql_text(a.sql_handle) b
OUTER APPLY sys.dm_exec_text_query_plan (a.plan_handle, a.statement_start_offset, a.statement_end_offset) c
LEFT JOIN sys.dm_exec_query_memory_grants m (nolock)
ON m.session_id = a.session_id
AND m.request_id = a.request_id
JOIN sys.databases d
ON d.database_id = a.database_id
WHERE  a.session_id = @@SPID --replace @@SPID with the SPID number for which you want to capture query plan
ORDER BY a.Start_Time
 

Hope this will be a good addition to your query bank.

Recently I came across a situation where queries are loading extremely slow from a table. After careful analysis we found the root cause being, a column with ntext datatype was getting inserted with huge amounts of text content/data. In our case DATALENGTH T-SQL function came real handy to know the actual size of the data in this column.

According to books online, DATALENGTH (expression) returns the length of the expression in bytes (or) the number of bytes SQL needed to store the expression which can be of any data type. From my experience this comes very handy to calculate length and size especially for LOB data type columns (varchar, varbinary, text, image, nvarchar, and ntext) as they can store variable length data. So, unlike LEN function which only returns the number of characters, the DATALENGTH function returns the actual bytes needed for the expression.

Here is a small example:

Use AdventureWorksLT2012
GO
Select ProductID, DATALENGTH(Name) AS SizeInBytes, LEN(Name) AS NumberOfCharacters
FROM [SalesLT].[Product]

 

–Results

DATALENGTH

If your column/expression size is too large like in my case, you can replace DATALENGTH(Name) with DATALENGTH(Name)/1024 to convert to KB or with DATALENGTH(Name)/1048576 to get the size in MB.

Most people prefer to have “sa”  account as the database owner, primary reason being sa login cannot be removed/deleted unlike any user account or service account and so the databases will never end-up in an orphaned stage.

I came-up with the below method to change the ownership to sa on all the 40 databases in our environment recently.

Step 1: Check the databases that does not have sa account as the owner

SELECT name AS DBName, suser_sname(owner_sid) AS DBOwner  
FROM sys.databases
WHERE suser_sname(owner_sid) <> 'sa'
 

Step 2: Generate the scripts to make sa account as owner for all the databases

SELECT 'ALTER AUTHORIZATION ON DATABASE::' + QUOTENAME(name) + ' TO [sa];'
from sys.databases
where name not in ('master', 'model', 'tempdb', 'msdb')
AND suser_sname(owner_sid) <> 'sa'
 

Step 3: Execute the result set from step 2 above to change the ownership to sa

--Sample result set from step2 above
ALTER AUTHORIZATION ON DATABASE::[AdventureWorksLT2012] TO [sa];
ALTER AUTHORIZATION ON DATABASE::[Northwind] TO [sa];
ALTER AUTHORIZATION ON DATABASE::[Pubs] TO [sa];
 

For more information on sa account you can check my previous blog post HERE

According to MSDN:

If the SQL Server service is running as a built-in account, such as Local System, Local Service, or Network Service, or a nondomain account, you must use certificates for endpoint authentication, and the Add New Replica wizard will be unable to create a database mirroring endpoint on the server instance. In this case, we recommend that you create the database mirroring endpoints manually before you launch the Add Replica to Availability Group Wizard.

The below message is displayed when we try to add replica with a nondomain account:

The Endpoints tab lists at least one endpoint that uses only Windows Authentication. However, the server instance might be running under a nondomain account. To use the listed endpoint, change the corresponding SQL Server service account to a domain account. To continue using the nondomain account, alter the endpoint to use a certificate. Do you want to use the listed endpoints?

One way to get around this issue without actually using a domain account is to grant access to the built-in account using the below script.


GRANT CONNECT ON endpoint::hadr_endpoint
TO [domain\servername$]

Note: If you do not have a end point, then you might have to create one for database mirroring as below.

 

CREATE ENDPOINT [Hadr_endpoint]
	STATE=STARTED
	AS TCP (LISTENER_PORT = 5022, LISTENER_IP = ALL)
	FOR DATA_MIRRORING (ROLE = ALL
, AUTHENTICATION = WINDOWS NEGOTIATE
, ENCRYPTION = REQUIRED ALGORITHM AES)

 

While I do not recommend you to use non domain account to configure AlwaysOn but this quick work around will get you through the blocking especially when you are configuring AlwaysOn for testing purposes.

Most of us know the default port for SQL Server is 1433, but there are various ports being used by SQL Server for other database services and SQL features.

In the below table I tried to list the ports that are frequently used by the Database Engine

Item Port
Default instance TCP port 1433
Named instance in default configuration Dynamic port. You can configure named instances to use fixed TCP ports
Dedicated Admin Connection (DAC) TCP port 1434
SQL Server Browser service UDP port 1434
SQL Server instance running over an  HTTP end-point TCP port 80 for CLEAR_PORT traffic   TCP port 443 for SSL_PORT traffic
Service Broker TCP port 4022
Replication TCP port 1433 for default instance
Transact-SQL Debugger TCP port 135
Analysis Services TCP port 2383 for default instance
Reporting Services Web Services TCP port 80
Reporting Services configured for use through HTTPS TCP port 443
Integration Services: Microsoft remote
procedure calls
TCP port 135
Integration services run time TCP port 135
Microsoft Distributed Transaction Coordinator (MS DTC) TCP port 135
SQL Server Management Studio browse connection to browser service UDP port 1434

You can find more information about the TCP and UDP ports SQL Server uses from books online here: Configure the Windows Firewall to Allow SQL Server Access

I have been noticing one very common error that occurs while trying to failover an Availability Group in SQL Server 2012 AlwaysON setup. The Availability Group fails to come online during a fail over process.

Here is the snippet of the error message.

error

Failed to bring availability group ‘availability_group‘ online. The operation timed out. Verify that the local Windows Server Failover Clustering (WSFC) node is online. Then verify that the availability group resource exists in the WSFC cluster. If the problem persists, you might need to drop the availability group and create it again.

This error is usually cause due to the lack of permission for [NT AUTHORITY\SYSTEM] account to create the high-availability group. Running the below SQL script in all the replica secondaries fixed this issue.

GRANT ALTER ANY AVAILABILITY GROUP TO [NT AUTHORITY\SYSTEM]
GO
GRANT CONNECT SQL TO [NT AUTHORITY\SYSTEM]
GO
GRANT VIEW SERVER STATE TO [NT AUTHORITY\SYSTEM]
GO

According to Microsoft, The [NT AUTHORITY\SYSTEM] account is used by SQL Server AlwaysOn health detection to connect to the SQL Server computer and to monitor health. When you create an availability group, health detection is initiated when the primary replica in the availability group comes online. If the [NT AUTHORITY\SYSTEM] account does not exist or does not have sufficient permissions, health detection cannot be initiated, and the availability group cannot come online during the creation process.

The below snippet shows that the NT AUTHORITY\SYSTEM runs sp_server_diagnostics which is a new internal procedure that runs on a continuous basis. This captures diagnostic data and health information about SQL Server to detect potential failures just like we had default trace (MSSQL\LOG\*.TRC) in the past

ALWAYSON ERROR

 

Hope this article helped you to understand the importance of the NT AUTHORITY\SYSTEM in AlwaysOn configured SQL 2012 servers.

via Failed to bring availability group ‘[availability group name]’ online.

Last week on one of our production servers (version 2011.110.3373.0), we’ve encountered a strange issue which is relatively new (only applicable for SQL Server 2012 and 2014 versions). Based on the symptoms observed and doing a quick Bing search found we encountered a product bug!

I observed multiple SPIDs, around 300+ running the same stored procedure which is doing an INSERT operation and are in a suspended status, they seemed to be hanging there for atleast like 45 minutes (usually they finish in few seconds). There is no blocking and I found nothing wrong with the SQL Server except for started seeing elevated values for PWAIT_MD_RELATION_CACHE and MD_LAZYCACHE_RWLOCK wait types. And, oh! I also noticed that tempdb data was at 99% full.

So I thought I found the root cause and tried mitigating the problem by adding extra tempdb space but still wasn’t any help. As the last resort I had to failover the services to another node, basically restarted SQL Server, to bring the server fully functional.

On further investigation we found the root cause as someone tried to create an index (online) to improve performance, but later he cancelled the create index and we hit this bug. However, this bug only effected the table on which index operation was attempted and so, everything else was operational except for that Stored Procedure running multiple SPIDs trying to INSERT to the table on which the user attempted CREATE INDEX command was blocked, impairing that part of functionality of the application.

Resolution: Cumulative Update 9 for SQL Server 2012 SP1; Cumulative Update 1 for SQL Server 2014

Here are more details about this problem: http://support.microsoft.com/kb/2926712

An auto-growth event is the process by which the SQL Server engine expands the size of a database file when it runs out of space. The amount by which a database file should grow is determined by the value that is set in the SQL configuration. While every organization has its own standards for this setting, however there are some widely followed best practices like for instance the auto-growth setting should not be in percent value

In this post I have put down two scripts that you can customize per your organizational standards. The first script helps you to identify the current settings and the second one can be used to update auto-growth settings. Both the scripts are targeted for all the databases by default, however you can call out the databases that you want to exclude from this change. Please make sure that you test these changes before pushing out to production servers.

Script 1: Identify the current database settings

select DB_NAME(mf.database_id) database_name
, mf.name logical_name
, CONVERT (DECIMAL (20,2) , (CONVERT(DECIMAL, size)/128)) [file_size_MB]
, CASE mf.is_percent_growth
WHEN 1 THEN 'Yes'
ELSE 'No'
END AS [is_percent_growth]
, CASE mf.is_percent_growth
WHEN 1 THEN CONVERT(VARCHAR, mf.growth) + '%'
WHEN 0 THEN CONVERT(VARCHAR, mf.growth/128) + ' MB'
END AS [growth_in_increment_of]
, CASE mf.is_percent_growth
WHEN 1 THEN
CONVERT(DECIMAL(20,2), (((CONVERT(DECIMAL, size)*growth)/100)*8)/1024)
WHEN 0 THEN
CONVERT(DECIMAL(20,2), (CONVERT(DECIMAL, growth)/128))
END AS [next_auto_growth_size_MB]
, CASE mf.max_size
WHEN 0 THEN 'No growth is allowed'
WHEN -1 THEN 'File will grow until the disk is full'
ELSE CONVERT(VARCHAR, mf.max_size)
END AS [max_size]
, physical_name
from sys.master_files mf

Script 2: Update database auto-growth values

/*
****MODIFICATION REQUIRED for AUTOGROWTH -- See line 64 below****
1) Use this script to change the auto growth setting of
   for all databases
2) If you want to exclude any database add the DBs in the
   WHERE Clause -- See line 50 below
3) Tested in 2012 and 2014 SQL Servers
*/

IF EXISTS(SELECT name FROM sys.sysobjects WHERE name = N'ConfigAutoGrowth' AND xtype='U')
DROP TABLE ConfigAutoGrowth
GO
CREATE TABLE DBO.ConfigAutoGrowth
(
iDBID INT,
sDBName SYSNAME,
vFileName VARCHAR(max),
vGrowthOption VARCHAR(12)
)
PRINT 'Table ConfigAutoGrowth Created'
GO
-- Inserting data into staging table
INSERT INTO DBO.ConfigAutoGrowth
SELECT
SD.database_id,
SD.name,
SF.name,
CASE SF.status
WHEN 1048576 THEN 'Percentage'
WHEN 0 THEN 'MB'
END AS 'GROWTH Option'
FROM SYS.SYSALTFILES SF
JOIN
SYS.DATABASES SD
ON
SD.database_id = SF.dbid
GO

-- Dynamically alters the file to set auto growth option to fixed mb
DECLARE @name VARCHAR ( max ) -- Database Name
DECLARE @dbid INT -- DBID
DECLARE @vFileName VARCHAR ( max ) -- Logical file name
DECLARE @vGrowthOption VARCHAR ( max ) -- Growth option
DECLARE @Query VARCHAR(max) -- Variable to store dynamic sql

DECLARE db_cursor CURSOR FOR
SELECT
idbid,sdbname,vfilename,vgrowthoption
FROM configautogrowth
--WHERE sdbname NOT IN ( 'master' ,'msdb' ) --<<--ADD DBs TO EXCLUDE
--AND vGrowthOption = 'Percentage' or 'Mb'

OPEN db_cursor
FETCH NEXT FROM db_cursor INTO @dbid,@name,@vfilename,@vgrowthoption
WHILE @@FETCH_STATUS = 0
BEGIN
PRINT 'Changing AutoGrowth option for database:- '+ UPPER(@name)

/******If you want to change the auto growth size from 100 to some other
value then just modify the filegrowth value in script at below location *********/

SET @Query = 'ALTER DATABASE '+ @name +'
MODIFY FILE (NAME = '+@vFileName+',FILEGROWTH = 5MB)' --<<--ADD AUTOGROWTH SIZE HERE

EXECUTE(@Query)

FETCH NEXT FROM db_cursor INTO @dbid,@name,@vfilename,@vgrowthoption
END
CLOSE db_cursor -- Closing the curson
DEALLOCATE db_cursor -- deallocating the cursor

GO
-- Querying system views to see if the changes are applied
DECLARE @SQL VARCHAR(8000), @sname VARCHAR(3)
SET @SQL=' USE ?
SELECT ''?'' [Dbname]
,[name] [Filename]
,CASE is_percent_growth
WHEN 1 THEN CONVERT(VARCHAR(5),growth)+''%''
ELSE CONVERT(VARCHAR(20),(growth/128))+'' MB''
END [Autogrow_Value]
,CASE max_size
WHEN -1 THEN CASE growth
WHEN 0 THEN CONVERT(VARCHAR(30),''Restricted'')
ELSE CONVERT(VARCHAR(30),''Unlimited'') END
ELSE CONVERT(VARCHAR(25),max_size/128)
END [Max_Size]
FROM ?.sys.database_files'

IF EXISTS(SELECT 1 FROM tempdb..sysobjects WHERE name='##Fdetails')
DROP TABLE ##Fdetails
CREATE TABLE ##Fdetails
(Dbname VARCHAR(50),Filename VARCHAR(50),
Autogrow_Value VARCHAR(15),Max_Size VARCHAR(30))
INSERT INTO ##Fdetails
EXEC sp_msforeachdb @SQL
SELECT * FROM ##Fdetails ORDER BY Dbname

--Dropping the staging table
DROP TABLE ConfigAutoGrowth
GO

In order to reduce Tempdb contention one of  the best practices is to maintain multiple sized Tempdb data files, matching the number of processors and up to a maximum of 8. In this post I will show you T-SQL script to identify current Tempdb configuration and number of logical processors along with adding additional Tempdb data files as required.

Script 1: Find current tempdb configuration


select DB_NAME(mf.database_id) database_name
, mf.name logical_name, mf.file_id
, CONVERT (DECIMAL (20,2)
, (CONVERT(DECIMAL, size)/128)) as [file_size_MB]
, CASE mf.is_percent_growth
WHEN 1 THEN 'Yes'
ELSE 'No'
END AS [is_percent_growth]
, CASE mf.is_percent_growth
WHEN 1 THEN CONVERT(VARCHAR, mf.growth) + '%'
WHEN 0 THEN CONVERT(VARCHAR, mf.growth/128) + ' MB'
END AS [growth_in_increment_of]
, CASE mf.is_percent_growth
WHEN 1 THEN CONVERT(DECIMAL(20,2)
,(((CONVERT(DECIMAL, size)*growth)/100)*8)/1024)
WHEN 0 THEN CONVERT(DECIMAL(20,2)
, (CONVERT(DECIMAL, growth)/128))
END AS [next_auto_growth_size_MB]
, physical_name from sys.master_files mf
where database_id =2 and type_desc= 'rows'

Script 2: Find number of logical processors

SELECT cpu_count AS logicalCPUs FROM sys.dm_os_sys_info

Script 3: Add tempdb data files as per processor count from the above query

ALTER DATABASE tempdb ADD FILE ( NAME = N'tempdev2',
FILENAME = N'D:\DBA\Data\tempdev2.ndf' , SIZE =8MB , FILEGROWTH = 5MB) --<<--Update the data file location/Size/AutoGrowth
GO

ALTER DATABASE tempdb ADD FILE ( NAME = N'tempdev3',
FILENAME = N'D:\DBA\Data\tempdev3.ndf' , SIZE =8MB , FILEGROWTH = 5MB)--<<--Update the data file location/Size/AutoGrowth
GO
---ETC, add files as per processors count

Reboot/Restart of SQL services is not required for making the tempdb changes. Here is a great post that explains how to best remove extra Tempdb files.

For more information:

 

Often times it is required to find out the SQL name from the host names in a clustered environment so you can use it to connect through SSMS. There are many ways you can achieve this, however I am showing 2 methods here. Method 1 is the most common way using Failover Cluster Manager (ideal when there is one or just a few servers) and second method focuses on getting the same information using PowerShell (Ideal when you are dealing with a large number of servers)

Method 1:

The easiest way (if not the fastest) is to load up the Failover Cluster Manager and go to each Failover Clustered instance to look for the virtual SQL names. You can also easily see which FCIs are running on a particular node by selecting a node and viewing what resources it currently owns as shown in the below snippets.

Poweshell_SQLVirtualName

This is the same for Windows 2003/ 2008+ and SQL 2005/ 2008.

Method 2:

While the above method is pretty easy, its not practical to log into each server to load up FCM when you have tens of hundreds of servers. For this you can use this simple PowerShell script that can be run remotely and can be fed with as many servers as you want to. This will output the SQL virtual names including those with named instances. Please note that the PowerShell cmdlets used here require admin rights on all of the nodes in the cluster or a security exception will be thrown.

Steps:

1.  Create a notepad file “TestServers” on your desktop that contains the list of servers (Host names) that you want to run the code against

2

2. Open Powershell with Admin Privileges

3. Use the below script to load the servers list  into a Variable (Copy & paste the below code in PowerShell and click Enter – Make sure to change the location of your text file)

$machines = get-content C:\Users\Desktop\testservers.txt 

4. Use the below script to call the servers from the above variable to get the output

import-module failoverclusters
foreach ($machine in $machines) {get-clusterresource -Cluster 
$machine -ErrorAction SilentlyContinue| where-object 
{$_.ResourceType -like ?SQL Server?}| 
get-clusterparameter VirtualServerName,InstanceName | 
group-object ClusterObject | select-object @{Name = ?SQLInstance?;
Expression = {[string]::join(?\?,($_.Group | 
select-object -expandproperty Value))}}} 
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