msdb Database

The msdb database is used by SQL Server Agent for scheduling alerts and jobs and by other features such as Service Broker and Database Mail. The sizes of msdb files may vary slightly for different editions of SQL Server Database Engine.

The following operations cannot be performed on the msdb database:

• Changing collation. The default collation is the server collation.
• Dropping the database.
• Dropping the guest user from the database.
• Enabling change data capture.
• Participating in database mirroring.
• Removing the primary filegroup, primary data file, or log file.
• Renaming the database or primary filegroup.
• Setting the database to OFFLINE.
• Setting the primary filegroup to READ_ONLY.

To know more about other System Databases Click Here

Wait Stats Cont..

For more information on the wait conditions firstly please refer this post

The below mentioned are basic explanations of each of the major wait types. Appearance of any of these wait types high up will certainly help direct your subsequent investigations.

CXPACKET

Often indicates nothing more than that certain queries are executing with parallelism; CXPACKET waits in the server are not an immediate sign of problems, although they may be the symptom of another problem, associated with one of the other high value wait types in the instance

SOS_SCHEDULER_YIELD

The tasks executing in the system are yielding the scheduler, having exceeded their quantum, and are having to wait in the runnable queue for other tasks to execute. This may indicate that the server is under CPU pressure

THREADPOOL

A task had to wait to have a worker bound to it, in order to execute. This could be a sign of worker thread starvation, requiring an increase in the number of CPUs in the server, to handle a highly concurrent workload, or it can be a sign of blocking, resulting in a large number of parallel tasks consuming the worker threads for long periods.

LCK_*

These wait types signify that blocking is occurring in the system and that sessions have had to wait to acquire a lock of a specific type, which was being held by another database session. This problem can be investigated further using the information in the sys.dm_db_index_operational_stats

PAGEIOLATCH_*, IO_COMPLETION, WRITELOG

These waits are commonly associated with disk I/O bottlenecks, though the root cause of the problem may be, and commonly is, a poorly performing query that is consuming excessive amounts of memory in the server. PAGEIOLATCH_* waits are specifically associated with delays in being able to read or write data from the database files. WRITELOG waits are related to issues with writing to log files. These waits should be evaluated in conjunction with the virtual file statistics as well as Physical Disk performance counters, to determine if the problem is specific to a single database, file, or disk, or is instance wide.

PAGELATCH_*

Non-I/O waits for latches on data pages in the buffer pool. A lot of times PAGELATCH_* waits are associated with allocation contention issues. One of the best-known allocations issues associated with PAGELATCH_* waits occurs in tempdb when the a large number of objects are being created and destroyed in tempdb and the system experiences contention on the Shared Global Allocation Map (SGAM), Global Allocation Map (GAM), and Page Free Space (PFS) pages in the tempdb database.

LATCH_*

These waits are associated with lightweight short-term synchronization objects that are used to protect access to internal caches, but not the buffer cache. These waits can indicate a range of problems, depending on the latch type. Determining the specific latch class that has the most accumulated wait time associated with it can be found by querying the sys.dm_os_latch_stats DMV.

ASYNC_NETWORK_IO

This wait is often incorrectly attributed to a network bottleneck. In fact, the most common cause of this wait is a client application that is performing row-by-row processing of the data being streamed from SQL Server as a result set (client accepts one row, processes, accepts next row, and so on). Correcting this wait type generally requires changing the client-side code so that it reads the result set as fast as possible, and then performs processing.

Good article on Performance Tuning SQL Database Performance Tuning for Developers

Another good article for Developers  MetaDapper: Data Mapping and Conversion Made Easy With the Right Tools

System Databases in SQL Server

System database in SQL Server are crucial, and you should leave them alone most of the time, The only exception to that rule is model database, which allows you to deploy changes such as stored procedures to any new database created. If a system database is tampered with or corrupted, you run the risk that SQL Server will not start. It contains all the stored procedures and tables needed for SQL Server to remain online.

master Database  – Records all the system-level information for an instance of SQL Server.

msdb Database – Is used by SQL Server Agent for scheduling alerts and jobs.

model Database – Is used as the template for all databases created on the instance of SQL Server. Modifications made to the model database, such as database size, collation, recovery model, and other database options, are applied to any databases created afterward.

Resource Database – Is a read-only database that contains system objects that are included with SQL Server. System objects are physically persisted in the Resource database, but they logically appear in the sys schema of every database.

tempdb Database – Is a workspace for holding temporary objects or intermediate result sets.

Alert me when SQL Server Drive Space is low

Keeping a watch on drive space on all Servers that you handle is a very integral part of DBA work. Once SQL Server runs out of disk on the underlying host, then everything obviously comes to a crashing halt. While proactively sizing data and log file sizes is the best technique to use when it comes to database sizing, there are still plenty of situations where some databases might need to be allowed to auto grow in many cases. As such, the last thing you want is for databases to grow to such a point that they run out of disk.

Below is a script that is very handy to avoid such catastrophic situations.  The below script has to be run in master database and a job has to be created to schedule running this procedure in  whatever frequency that is acceptable to you.

This script checks for drive space that is below 5% and fires an alert to the specified email address if the drive space is below 5%.

USE [master]
GO
/****** Object: StoredProcedure [dbo].[up_diskspace] ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
-- EXEC up_diskspace
CREATE PROCEDURE [dbo].[up_diskspace] 
AS 
SET NOCOUNT ON 
DECLARE @emailBody NVARCHAR(MAX)
 , @emailSubject VARCHAR(50)
 , @emailDate VARCHAR(10)
 , @serverName VARCHAR(100)
 , @runStatusChar VARCHAR(20)
 , @OK_serverList NVARCHAR(MAX)
 , @serverOK VARCHAR(100)
 , @sendEmail INT
 , @jobRunDateChar CHAR(8)
 , @listStart TINYINT
 , @hr int 
 , @fso int 
 , @drive char(1) 
 , @odrive int 
 , @TotalSize varchar(20) 
 , @MB bigint 
 , @freeSpace VARCHAR(10); 
SET @MB = 1048576
SET @listStart = 1
SET @emailSubject = 'UAT - Low Drive Space Alert!'
SET @serverName = @@serverName
SET @sendEmail = 0
CREATE TABLE #drives (drive char(1) PRIMARY KEY, 
 FreeSpace int NULL, 
 TotalSize int NULL) 
INSERT #drives(drive,FreeSpace) 
EXEC master.dbo.xp_fixeddrives 
EXEC @hr=sp_OACreate 'Scripting.FileSystemObject',@fso OUT 
IF @hr <> 0 EXEC sp_OAGetErrorInfo @fso 
DECLARE dcur CURSOR LOCAL FAST_FORWARD 
FOR SELECT drive from #drives 
ORDER by drive 
OPEN dcur 
FETCH NEXT FROM dcur INTO @drive 
WHILE @@FETCH_STATUS=0 
BEGIN 
 EXEC @hr = sp_OAMethod @fso,'GetDrive', @odrive OUT, @drive 
 IF @hr <> 0 EXEC sp_OAGetErrorInfo @fso 
 EXEC @hr = sp_OAGetProperty @odrive,'TotalSize', @TotalSize OUT 
 IF @hr <> 0 EXEC sp_OAGetErrorInfo @odrive 
 UPDATE #drives 
 SET TotalSize=@TotalSize/@MB 
 WHERE drive=@drive 
 FETCH NEXT FROM dcur INTO @drive 
END 
CLOSE dcur 
DEALLOCATE dcur 
EXEC @hr=sp_OADestroy @fso 
IF @hr <> 0 EXEC sp_OAGetErrorInfo @fso 
SELECT drive, 
 FreeSpace as 'Free(MB)', 
 TotalSize as 'Total(MB)', 
 CAST((FreeSpace/(TotalSize*1.0))*100.0 as int) as 'Free(%)' 
INTO #freeSpace
FROM #drives
ORDER BY drive 
--SELECT * FROM #freeSpace
DELETE #freeSpace
WHERE [Free(%)] > 5
SET @sendEmail = (SELECT count(*) FROM #freeSpace)
IF @sendEmail > 0 
BEGIN
 --GET DRIVES WITH LESS THAN 5% DISK FREE SPACE
 DECLARE l CURSOR FORWARD_ONLY
 FOR SELECT drive, [Free(MB)] FROM #freeSpace
 OPEN l -- The keyset is copied to tempdb
 FETCH l INTO @drive, @freeSpace
 WHILE (@@FETCH_STATUS = 0) 
 BEGIN
 IF @listStart = 1
 BEGIN
 SET @OK_serverList = @drive + ' (' + @freeSpace + ' MB)'
 SET @listStart = 0
 END
 ELSE
 SET @OK_serverList = @OK_serverList + ', ' + @drive + ' (' + @freeSpace + ' MB)'
 FETCH l INTO @drive, @freeSpace
 END
 CLOSE l
 DEALLOCATE l
 -- RESET @listStart
 SET @listStart = 1
 SET @OK_serverList = @OK_serverList + '.'
 -- PRINT LIST
 SET @emailBody = CHAR(13) + CHAR(13) + 'The following drive(s) on ' + @serverName + ' are below 5% free space: ' + ISNULL(@OK_serverList, '')
 --- EMAIL REPORT
 EXEC msdb.dbo.sp_send_dbmail 
 @recipients = 'SANTHOSHVISWANATHAN@GMAIL.COM'
 , @body = @emailBody
 , @subject = @emailSubject
 , @importance = 'HIGH'
END
DROP TABLE #drives 
DROP TABLE #freeSpace
RETURN

Please check the link for Mail alerts for new added record.

Understanding “login failed” – Error 18456 in SQL Server

We are looking at the “login failed” error in SQL Server today.

Msg 18456, Level 14, State X, Server <server name>, Line 1
Login failed for user ‘<user name>’

It’s a fairly common error we receive while logging into. If you do some research on this, you will find that your connection request was successfully received by the server you specified , but the server is not able to grant you access for a number of reasons and throws error: 18456.

If Error 18456 occurs, it will have an error state number that can help determine the cause. Obtaining information on the error state can make troubleshooting significantly easier.

The Error state descriptions are as follows:

State 2 and State 5 – Invalid USERID was used to log in.
State 6 – Attempt to use a Windows login name with SQL Authentication
State 7 – Login is disabled and password could be mismatched.
State 8 – Password mismatch has occurred.
State 9 – Invalid password.
State 11 and 12 – Valid login but server access failure
State 13 – SQL Server service is paused.
State 18 – Change of password is required.

Find Service Pack and Version of SQL Server

Query to find the service pack and version of SQL Server you are using. Click here to find the version list

SELECT 
SERVERPROPERTY('servername') as Servername, 
SERVERPROPERTY('productversion') as Version, 
SERVERPROPERTY ('productlevel') as ServicePack, 
SERVERPROPERTY ('edition') as Edition

Microsoft SQL Server Version List

Quick Summary

Click here to find the version of SQL Server you are using.

CTP  : Community Technology Preview (beta release)
RC    : Release Candidate
RTM : Released To Manufacturing; It is the original, released build version of the product, i.e. what you get on the DVD or when you download the ISO file from MSDN.
CU    :Cumulative Update; Cumulative updates contain the bug fixes and enhancements–up to that point in time–that have been added since the previous Service Pack release and will be contained in the next service pack release. Installation of the Cumulative Update is similar to the installation of a Service Pack. Cumulative Updates are not fully regression tested.
SP     : Service Pack; much larger collection of hotfixes that have been fully regression tested. In some cases delivers product enhancements.
GDR  :  General Distribution Release; GDR fixes should not contain any of the CU updates.
QFE   : Quick Fix Engineering; QFE updates include CU fixes.

 

Ref: sqlserverbuilds