SQLDBA- SQL Server Wait Events

 

To solve slowness of SQL Server database, you should find which wait events exists in the database.

You can find wait events of database with following query.

with waits as
(select
wait_type,
wait_time_ms / 1000.0 as waits,
(wait_time_ms - signal_wait_time_ms) / 1000.0 as resources,
signal_wait_time_ms / 1000.0 as signals,
waiting_tasks_count as waitcount,
100.0 * wait_time_ms / sum (COALESCE (wait_time_ms,1)) over() as percentage,
row_number() over(order by wait_time_ms desc) as rownum
from sys.dm_os_wait_stats
where wait_type not in (
N'CLR_SEMAPHORE', N'LAZYWRITER_SLEEP',
N'RESOURCE_QUEUE', N'SQLTRACE_BUFFER_FLUSH',
N'SLEEP_TASK', N'SLEEP_SYSTEMTASK',
N'WAITFOR', N'HADR_FILESTREAM_IOMGR_IOCOMPLETION',
N'CHECKPOINT_QUEUE', N'REQUEST_FOR_DEADLOCK_SEARCH',
N'XE_TIMER_EVENT', N'XE_DISPATCHER_JOIN',
N'LOGMGR_QUEUE', N'FT_IFTS_SCHEDULER_IDLE_WAIT',
N'BROKER_TASK_STOP', N'CLR_MANUAL_EVENT',
N'CLR_AUTO_EVENT', N'DISPATCHER_QUEUE_SEMAPHORE',
N'TRACEWRITE', N'XE_DISPATCHER_WAIT',
N'BROKER_TO_FLUSH', N'BROKER_EVENTHANDLER',
N'FT_IFTSHC_MUTEX', N'SQLTRACE_INCREMENTAL_FLUSH_SLEEP',
N'DIRTY_PAGE_POLL', N'SP_SERVER_DIAGNOSTICS_SLEEP')
)
select
w1.wait_type as waittype, 
cast (w1.waits as decimal(14, 2)) wait_s,
cast (w1.resources as decimal(14, 2)) resource_s,
cast (w1.signals as decimal(14, 2)) signal_s,
w1.waitcount wait_count,
cast (w1.percentage as decimal(4, 2)) percentage,
cast ((w1.waits / w1.waitcount) as decimal (14, 4)) avgWait_s,
cast ((w1.resources / w1.waitcount) as decimal (14, 4)) avgResource_s,
cast ((w1.signals / w1.waitcount) as decimal (14, 4)) avgSignal_s
from waits as w1
inner join waits as w2 on w2.rownum <= w1.rownum
group by w1.rownum, w1.wait_type, w1.waits, w1.resources, w1.signals, w1.waitcount, w1.percentage
having sum (w2.percentage) - w1.percentage < 95; -- percentage threshold

You can get list and status of currently waiting tasks with following script.

select wt.session_id, wt.exec_context_id, wt.wait_duration_ms, wt.wait_type, wt.blocking_session_id, wt.resource_address, wt.resource_description, s.program_name, st.text, sp.query_plan, s.cpu_time cpu_time_ms, s.memory_usage*8 memory_usage_kb
from sys.dm_os_waiting_tasks wt
join sys.dm_exec_sessions s on s.session_id=wt.session_id
join sys.dm_exec_requests r on r.session_id=s.session_id
outer apply sys.dm_exec_sql_text(r.sql_handle) st
outer apply sys.dm_exec_query_plan(r.plan_handle) sp
where s.is_user_process=1
order by wt.session_id, wt.exec_context_id

You can find wait events of database with following query.

SELECT getdate() as 'Run_Time' --script running time
    , wait_type --wait type
    ,waiting_tasks_count
, CAST(wait_time_ms / 1000. AS DECIMAL(12, 2)) AS wait_time_s --saniye cinsinden bekleme zamaný
, CAST(100. * wait_time_ms / SUM(wait_time_ms) OVER() AS DECIMAL(12, 2)) AS pct --toplam beklemeye oraný
FROM sys.dm_os_wait_stats
WHERE wait_type NOT IN ('BROKER_TASK_STOP','Total','SLEEP','BROKER_EVENTHANDLER','BROKER_RECEIVE_WAITFOR',
      'BROKER_TRANSMITTER','CHECKPOINT_QUEUE','CHKPT,CLR_AUTO_EVENT','CLR_MANUAL_EVENT','KSOURCE_WAKEUP','LAZYWRITER_SLEEP',
      'LOGMGR_QUEUE','ONDEMAND_TASK_QUEUE','REQUEST_FOR_DEADLOCK_SEARCH','RESOURCE_QUEUE','SERVER_IDLE_CHECK',
      'SLEEP_BPOOL_FLUSH','SLEEP_DBSTARTUP','SLEEP_DCOMSTARTUP','SLEEP_MSDBSTARTUP','SLEEP_SYSTEMTASK','SLEEP_TASK',
      'SLEEP_TEMPDBSTARTUP','SNI_HTTP_ACCEPT','SQLTRACE_BUFFER_FLUSH','TRACEWRITE','WAIT_FOR_RESULTS','WAITFOR_TASKSHUTDOWN',
       'XE_DISPATCHER_WAIT','XE_TIMER_EVENT','WAITFOR')
ORDER BY 4 DESC

SQLDBA- Generate the ALTER script for set compatibility for all databases

 

-- Alter  script set  compatibility y to sql server  2022

DECLARE @DBName SYSNAME;

DECLARE @SQL NVARCHAR(MAX);

-- Table variable to hold database names

DECLARE @DBList TABLE (DBName SYSNAME);

-- Insert all user databases except system ones

INSERT INTO @DBList (DBName)

SELECT name FROM sys.databases

WHERE database_id > 4 -- Exclude system DBs

AND state_desc = 'ONLINE';

-- Initialize loop

WHILE EXISTS (SELECT 1 FROM @DBList)

BEGIN

    -- Get one database name

    SELECT TOP 1 @DBName = DBName FROM @DBList;

    -- Build and execute the ALTER statement

    SET @SQL = 'ALTER DATABASE [' + @DBName + '] SET COMPATIBILITY_LEVEL = 160;';

    PRINT 'Updating compatibility for: ' + @DBName;

PRINT @SQL

    --EXEC sp_executesql @SQL;

    -- Remove processed DB

    DELETE FROM @DBList WHERE DBName = @DBName;

END

--Set  compatability  to  SQL server  2022

 SELECT 'ALTER DATABASE [' +  name+ '] SET COMPATIBILITY_LEVEL = 160

 GO' FROM sys.databases

WHERE name IN ( 

 'master'

)

-- Roll back script

 SELECT 'ALTER DATABASE [' +  name+ '] SET COMPATIBILITY_LEVEL = '+CONVERT(VARCHAR(5),compatibility_level) +'

 GO' FROM sys.databases

WHERE name IN ( 

 'master'

)

SQLDBA - Script to Loop through all the transaction log file and restore them automatically.

 

Script to Loop through all the transaction log file and restore them automatically.

Below script is generating the restoring the  transactional log backups.  Initially  we have inserted transaction files into  temp table and then we have generating restoring the tractional log backup.

Method1:

USE master;

DECLARE @t AS TABLE (fname VARCHAR(max));

INSERT @t EXEC xp_cmdshell 'dir /b /S E:\dirname\*.trn';

SELECT 'RESTORE LOG [DBNAME] FROM DISK = ''' + fname + ''' WITH NORECOVERY;' FROM @t WHERE fname IS NOT NULL

Method2:

Powershell  Script;

To automatically loop through and restore all SQL Server transaction log files (.trn), you can use a PowerShell script or T-SQL script depending on your environment and preferences. Here's a PowerShell script that reads all .trn files from a folder and restores them in sequence.

# Define variables
$serverName = "YourSQLServerInstance"  
$databaseName = "YourDatabase"  
$backupFolder = "C:\Backups\Logs"
$restoreDatabase = $false  # Set to $true if you want to restore the full DB first

# Optional: Restore full backup if needed
if ($restoreDatabase) {
    $fullBackupFile = "C:\Backups\YourDatabase.bak"
    Invoke-Sqlcmd -ServerInstance $serverName -Query "
        RESTORE DATABASE [$databaseName]
        FROM DISK = N'$fullBackupFile'
        WITH NORECOVERY, REPLACE"
}

# Get all .trn files sorted by creation time
$logFiles = Get-ChildItem -Path $backupFolder -Filter *.trn | Sort-Object LastWriteTime

# Loop through and restore each log file
foreach ($file in $logFiles) {
    Write-Host "Restoring log file: $($file.Name)"
    Invoke-Sqlcmd -ServerInstance $serverName -Query "
        RESTORE LOG [$databaseName]
        FROM DISK = N'$($file.FullName)'
        WITH NORECOVERY"
}

# Finally, recover the database
Invoke-Sqlcmd -ServerInstance $serverName -Query "
    RESTORE DATABASE [$databaseName] WITH RECOVERY"

Write-Host "Transaction log restore completed."

Method3:

# Define parameters
$serverInstance = "localhost\SQLEXPRESS"  # Change to your SQL Server instance
$databaseName = "YourDatabaseName"        # Change to your target database
$logBackupFolder = "C:\LogBackups"        # Folder containing .trn files

# Load SQL Server SMO
Add-Type -AssemblyName "Microsoft.SqlServer.SMO"
Add-Type -AssemblyName "Microsoft.SqlServer.ConnectionInfo"
Add-Type -AssemblyName "Microsoft.SqlServer.SmoExtended"

# Connect to SQL Server
$server = New-Object Microsoft.SqlServer.Management.Smo.Server $serverInstance

# Get all .trn files sorted by name (assuming naming reflects order)
$logFiles = Get-ChildItem -Path $logBackupFolder -Filter *.trn | Sort-Object Name

foreach ($logFile in $logFiles) {
    Write-Host "Restoring log file: $($logFile.Name)"

    $restore = New-Object Microsoft.SqlServer.Management.Smo.Restore
    $restore.Action = "Log"
    $restore.Database = $databaseName
    $restore.Devices.AddDevice($logFile.FullName, "File")
    $restore.NoRecovery = $true  # Keep in restoring state for next log

    try {
        $restore.SqlRestore($server)
        Write-Host "Successfully restored: $($logFile.Name)"
    } catch {
        Write-Host "Failed to restore: $($logFile.Name)"
        Write-Host $_.Exception.Message
    }
}

Write-Host "All log files processed."

SQL DBA - Find the job names with user name with running as job owner.

 

-- Find the job names with user name with running as job owner. 

SELECT j.name AS JobName,

       j.owner_sid,

       s.name AS JobOwner,

       a.start_execution_date

FROM msdb.dbo.sysjobs AS j

INNER JOIN msdb.dbo.sysjobactivity AS a

    ON j.job_id = a.job_id

INNER JOIN sys.server_principals AS s

    ON j.owner_sid = s.sid

WHERE a.run_requested_date IS NOT NULL

  AND a.stop_execution_date IS NULL  -- Job is still running

  AND s.name LIKE  '%SVC_%';       -- Replace with the specific user

-- Find the job name, with command context . 

SELECT j.name AS JobName,

       js.step_id,

       js.step_name,

       js.database_name,

       js.command,

       js.subsystem

FROM msdb.dbo.sysjobs AS j

INNER JOIN msdb.dbo.sysjobsteps AS js

    ON j.job_id = js.job_id

WHERE js.command LIKE '%SVC%';

SQLDBA- How to verify the CDC is enabled data bases or tables

How to  verify the CDC is enabled data bases or tables

The following query  will get list  of  CDC enabled data bases 

SELECT

    name AS DatabaseName,

    is_cdc_enabled

FROM sys.databases

WHERE is_cdc_enabled = 1;

The following query  will get list  of  CDC enabled  tables  with in the  database. 

USE <DB Name>;  -- Replace with actual DB name

GO

SELECT 

    s.name AS SchemaName,

    t.name AS TableName,

    c.capture_instance,

    c.supports_net_changes,

    c.start_lsn,

    c.end_lsn

FROM 

    cdc.change_tables c

JOIN 

    sys.tables t ON c.source_object_id = t.object_id

JOIN 

    sys.schemas s ON t.schema_id = s.schema_id;

Below will get the list of tables which  are enabled CDC from all data bases. 

DECLARE @dbName NVARCHAR(128)

DECLARE @sql NVARCHAR(MAX)

-- Cursor to loop through all CDC-enabled databases

DECLARE db_cursor CURSOR FOR

SELECT name FROM sys.databases WHERE is_cdc_enabled = 1

OPEN db_cursor

FETCH NEXT FROM db_cursor INTO @dbName

WHILE @@FETCH_STATUS = 0

BEGIN

    PRINT 'Checking CDC tables in database: ' + @dbName

    SET @sql = '

    USE [' + @dbName + '];

    IF EXISTS (SELECT 1 FROM sys.tables WHERE is_tracked_by_cdc = 1)

    BEGIN

        SELECT 

            ''' + @dbName + ''' AS DatabaseName,

            s.name AS SchemaName,

            t.name AS TableName,

            c.capture_instance,

            c.supports_net_changes,

            c.start_lsn,

            c.end_lsn

        FROM 

            cdc.change_tables c

        JOIN 

            sys.tables t ON c.source_object_id = t.object_id

        JOIN 

            sys.schemas s ON t.schema_id = s.schema_id;

    END

    ELSE

    BEGIN

        PRINT ''No CDC-enabled tables found in database: ' + @dbName + '''

    END

    '

    EXEC sp_executesql @sql

    FETCH NEXT FROM db_cursor INTO @dbName

END

CLOSE db_cursor

DEALLOCATE db_cursor

DBA- Server Login name , DB login name along with their roles/memebers in sql server

 

Below Query  help  bring the  server  login name , data base level login name  along with their roles/members. 

This query will help us to validate the roles/ members are mapped correctly or not. 

USE master 

GO

CREATE TABLE #temp

(

id INTEGER  IDENTITY(1,1),

DatabasseName VARCHAR(100),

login_name VARCHAR(500),

database_user VARCHAR(500),

role_name VARCHAR(500),

user_type VARCHAR(500),

authentication_type_desc VARCHAR(500)

)

EXEC sp_foreachdb 

'

USE ?

INSERT INTO #temp (DatabasseName,login_name,database_user,role_name,user_type,authentication_type_desc)

SELECT

''?'' AS DatabasseName,

    sp.name AS login_name,

    dp.name AS database_user,

    dr.name AS role_name,

    dp.type_desc AS user_type,

    dp.authentication_type_desc

FROM 

    sys.server_principals sp

 JOIN  

    sys.database_principals dp ON sp.sid = dp.sid

LEFT JOIN 

    sys.database_role_members drm ON dp.principal_id = drm.member_principal_id

LEFT JOIN 

    sys.database_principals dr ON drm.role_principal_id = dr.principal_id

WHERE 

    sp.type IN (''S'',''U'', ''G'') AND dp.type IN (''S'', ''U'', ''G'')

ORDER BY 

    sp.name, dr.name 

'

SELECT  *  FROM #temp

WHERE login_name ='svcTMWorks-trng' 

--- DB Login names with their roles

SELECT

    sp.name AS login_name,

    dp.name AS database_user,

    dr.name AS role_name,

    dp.type_desc AS user_type,

    dp.authentication_type_desc

FROM 

    sys.server_principals sp

LEFT JOIN  

    sys.database_principals dp ON sp.sid = dp.sid

LEFT JOIN 

    sys.database_role_members drm ON dp.principal_id = drm.member_principal_id

LEFT JOIN 

    sys.database_principals dr ON drm.role_principal_id = dr.principal_id

WHERE 

    sp.type IN ('S', 'U', 'G') AND dp.type IN ('S', 'U', 'G')

AND sp.name  ='svcTMWorks-trng'

ORDER BY 

    sp.name, dr.name;

SQLDBA- how to know the created index file group name with T-SQL

 Hello, 

To determine the filegroup where an index is created in SQL Server, you can use the following methods:

1. Using sys.indexes and sys.filegroups System Views

You can query the system views to find the filegroup of an index:

Sql
SELECT 
    i.name AS IndexName,
    o.name AS TableName,
    f.name AS FileGroupName
FROM 
    sys.indexes i
JOIN 
    sys.objects o ON i.object_id = o.object_id
JOIN 
    sys.data_spaces f ON i.data_space_id = f.data_space_id
WHERE 
    o.type = 'U'; -- Only user tables

This query will list all indexes, their associated tables, and the filegroups they belong to.

2. Using SQL Server Management Studio (SSMS)

1. Open SSMS and connect to your database.
2. Navigate to the table where the index is created.
3. Expand the Indexes folder under the table.
4. Right-click the index and select Properties.
5. In the Storage section, you can see the filegroup where the index is stored.

3. Using sp_helpindex

You can use the sp_helpindex system stored procedure to get details about indexes on a specific table:

Sql
EXEC sp_helpindex 'YourTableName';

This will return information about the indexes on the table, including their names and types. However, it does not directly show the filegroup. For filegroup details, use the first method.