Wednesday, March 28, 2012

SQL Server 2012 Tutorials and Sample Databases

Microsoft SQL Server 2012 has released RTM recently. No doubt that you're interested to learn new features of the new version. If so then it is useful to have the tutorials and sample databases installed on your server. You can get them using below links;

Tutorials here

Sample Databases here

Note that sample databases are just data files (No log file). You need to attach it to your server to create the databases. Use the following T-SQL script.

CREATE DATABASE AdventureWorks2012
ON (FILENAME = 'D:\SQL Server\DATA\AdventureWorks2012_Data.mdf')

Enjoy with the new version of SQL Server.

Saturday, March 24, 2012

Reasons that can not reclaim transaction log space

The best practice is to setup log backups periodically (if the database is not in SIMPLE recovery) in order to keep the database log size minimum. However there are some occasions even the log backup is setup, the log size keeps growing. To find out the reason you can refer, log_reuse_wait in sys.databases.

As per MSDN, log_reuse_wait is as follows; Also look at the log_reuse_wait_desc column for more detail.

Reuse of transaction log space is currently waiting on one of the following:
0 = Nothing
1 = Checkpoint
2 = Log backup
3 = Active backup or restore
4 = Active transaction
5 = Database mirroring
6 = Replication
7 = Database snapshot creation
8 = Log Scan
9 = Other (transient)

Cheers for reading this blog post.

Wednesday, March 21, 2012

How to get the execution plan of a stored procedure?

Think about a situation where you have identified a badly performing stored procedure in Production environment and now you want to see the execution plan of it for further analysis. Please note, executing the procedure with sample parameter values in Production environment should be done with extra care because if the procedure is only SELECT then no issue but if it has DML operations, then issue.

You can use following DMVs to get the execution plan either XML format or graphical one.

USE AdventureWorks2008R2

EXEC [dbo].[uspGetEmployeeManagers] @BusinessEntityID=60
Note: I executed the SP first so that plan will be created. In actual environment this is not necessary.

select Plan_handle from sys.dm_exec_procedure_stats ps
where ps.database_id=DB_ID('AdventureWorks2008R2')
              and object_id=object_id('dbo.uspGetEmployeeManagers')  

--Copy and paste the plan handle to the below query
select * from sys.dm_exec_query_plan(0x05000500EAE8807F40E13287000000000000000000000000)

Cheers for reading this blog post.

Friday, March 16, 2012

Multi-Subnet Clustering

This is a new feature in SQL Server 2012. However Windows 2008 has this feature. With the introduction of the new feature, SQL Server can have a cluster node in a different subnet. Subnet is a virtual grouping concept available in network. Subnet will enable network administrators to manage networks effectively over geographical areas. 

Since the subnet is a geographical network concept, now SQL Server clustering can be used as DR (Disaster Recovery) solution than ever before. 

More information can be found here.

Tuesday, March 6, 2012

Parameter Sniffing

What is it? First we will go through the scripts below;

Create the following index;

USE [AdventureWorks2008R2]

/****** Object:  Index [NNI_SalesOrderDetail_ModifiedDate]    Script Date: 03/06/2012 15:09:41 ******/
CREATE NONCLUSTERED INDEX [NNI_SalesOrderDetail_ModifiedDate] ON [Sales].[SalesOrderDetail]
     [ModifiedDate] ASC

Then create the below stored procedure. It is a very simple SP which has single SELECT statement for Sales.SalesOrderDetail table. There are two parameters for two date values.

Friday, March 2, 2012

VLDBs backup in few seconds

VLDB - Very Large Databases, like several Gigs of databases. (50GB, 100GB, etc) How about managing backups? You may need to spend 20-30 hours to take a full backup of such DBs. Of course SQL Server 2008 has improved backup system than its earlier versions. Another alternative method would be to use third party tools like, LiteSpeed or RedGate backups. But stills you can't make it in few seconds. How about a system to take such a large DB backup in a few seconds? ANSWER is to use SAN snapshot backup.

How to interpret Disk Latency

I was analyzing IO stats in one of our SQL Servers and noticed that IO latency (Read / Write) are very high. As a rule of thumb, we know tha...