Category Archives: SQL Server 2014

Spinlocks lightweight synchronization primitives

Spinlocks are lightweight synchronization primitives which are used to protect access to data structures. Spinlocks are used to access data structures for a very short period of time. When a thread attempting to acquire a spinlock and if it is unable to obtain access it executes in a loop periodically checking to determine if the resource is available instead of immediately yielding.

After some period of time a thread waiting on a spinlock will yield before it is able to acquire the resource in order to allow other threads running on the same CPU to execute. This is known as a backoff.

When a large number of threads are contending for access to a single spinlock and it can lead to performance problems

You can use below DMV to get the SPIN LOCK information

select * from sys.dm_os_spinlock_stats

Examples
FGCP_PRP_FILL
OPT_IDX_STATS
BUF_FREE_LIST

Script to get data file size, used space and free space

While troubleshooting the disk space issue, you can use below script to check the data file size, used space and free size.

select 
		DBName,
		name,
		[filename],
		size as 'Size(MB)',
		usedspace as 'UsedSpace(MB)',
		(size - usedspace) as 'AvailableFreeSpace(MB)'
from		
(	
SELECT
db_name(s.database_id) as DBName,
s.name AS [Name],
s.physical_name AS [FileName],
(s.size * CONVERT(float,8))/1024 AS [Size],
(CAST(CASE s.type WHEN 2 THEN 0 ELSE CAST(FILEPROPERTY(s.name, 'SpaceUsed') AS float)* CONVERT(float,8) END AS float))/1024 AS [UsedSpace],
s.file_id AS [ID]
FROM
sys.filegroups AS g
INNER JOIN sys.master_files AS s ON ((s.type = 2 or s.type = 0) and s.database_id = db_id() and (s.drop_lsn IS NULL)) AND (s.data_space_id=g.data_space_id)
) DBFileSizeInfo


Stripping SQL Server Database Backup to Multiple Files

Stripping Database backup to multiple files and on different drives will make the backup speed faster and will reduce the backup duration.

Check the below sample script for the backup and restore. You can perform the same task using SSMS GUI as well.
Backup Script

BACKUP DATABASE [SQLDBPool] TO  
DISK = N'C:\JSpace\Backup\SQLDBPool1.bak',  
DISK = N'C:\JSpace\Backup\SQLDBPool2.bak',  
DISK = N'C:\JSpace\Backup\SQLDBPool3.bak'
WITH NOFORMAT, 
NOINIT,  
NAME = N'SQLDBPool-Full Database Backup', SKIP, NOREWIND, NOUNLOAD,  STATS = 10
GO

Restore Script

RESTORE DATABASE [SQLDBPool] FROM  
DISK = N'C:\JSpace\Backup\SQLDBPool1.bak',  
DISK = N'C:\JSpace\Backup\SQLDBPool2.bak',  
DISK = N'C:\JSpace\Backup\SQLDBPool3.bak'
WITH  FILE = 1,  NOUNLOAD,  STATS = 10,replace
GO

Script to find out the traces running on SQL Server instance

You can execute the below script on SQL Server instance to find out the traces, trace type, trace file path and trace status.

select
      TraceType =
       case trace.is_default
            when 1 THEN 'Default/System Trace'
            when 0 THEN 'User Trace'
       end,
      Trace_Status =
      case trace.status
            when 1 THEN 'Running'
            when 0 THEN 'Stopped'
      end,
       ssion.session_id as SessionID,
       [loginName] = coalesce(ssion.login_name,ssion.login_name,'Reader SPID Not mentioned'),
       [Trace_File_Path] = coalesce(trace.[Path],trace.[Path],'OLEDB Client Trace')
      from sys.traces trace
            left join sys.dm_exec_sessions ssion on trace.reader_spid = ssion.session_id

How to attach a SQL Server database with a missing transaction log file?

There may be situation where the transaction log file is corrupted or delete due to some issue, there is still hope to recover the database using data file. In the below script we will create the scenario and recover the database using data file only.

-- create the below sample database
create database [SQLDBPool_5] 

-- execute the command to get the data log file location
sp_helpdb sqlhelpdesk

-- Copy the location of log file and data file from the output of the above command
-- C:\JSpace\sqldbpool_5_log.ldf, C:\JSpace\sqldbpool_5.mdf

-- Detatch the database
USE [master]
GO
ALTER DATABASE [SQLDBPool_5] SET  SINGLE_USER WITH ROLLBACK IMMEDIATE
GO
USE [master]
GO
EXEC master.dbo.sp_detach_db @dbname = N'SQLDBPool_5'
GO

-- Delete the log file
xp_cmdshell 'del "c:\JSpace\SQLDBPool_5_log.ldf"'


-- attach the database using MDF file only SQL Server will create the log file its self
USE [master]
GO
CREATE DATABASE [SQLDBPool_5]  ON 
( FILENAME = N'C:\JSpace\sqldbpool_5.mdf' )
FOR ATTACH
GO

-- You will the below message on the execution of the above command
/*
File activation failure. The physical file name "c:\JSpace\SQLDBPool_5_log.ldf" may be incorrect.
New log file 'c:\JSpace\SQLDBPool_5_log.ldf' was created.
*/