DBA WORLD

18 July 2011

SQL Server 2008 R2 -Uninstall issues

Go to this registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

Assume need to unintall the "Microsoft SQL Server 2008 Database Engine Shared",

* Search for SQL Server 2008 keys in the uninstall registry.
* Keep searching until you find the Database engine shared install location
Note the “Install source”, copy the path and access that path via Start :: Run
* Right click on the msi and choose uninstall.

Truncate LOG- Replication

Truncating the log of a previously replicated database

(The following is specific to SQL Server 2000 and might not apply to more recent versions.)

I occasionally restore production databases to a test system. Normally I just flip the recovery model from full and simple and I’m good to go. Unfortunately, if the database was being replicated it’s not so easy.

Even if you restore the database without “KEEP REPLICATION”, which would imply all the replication bits would be cleaned up for you, the transaction log will still have a replication marker that prevents it from being truncated. This means the log file, even in “simple” mode, will grow unbounded (not good!).

I’m always reminded of this when I try to clean up an ever-growing log with this command:

BACKUP LOG yourdb WITH TRUNCATE_ONLY

and I get this error:

The log was not truncated because records at the beginning of the log are pending replication. Ensure the Log Reader Agent is running or use sp_repldone to mark transactions as distributed

Not one to ignore the advice of error messages, I then try running the following commands:

-- see what's going on
DBCC OPENTRAN

-- not too much? just clear the replication marker
EXEC sp_repldone @xactid = NULL,
@xact_seqno = NULL,
@numtrans = 0,
@time = 0,
@reset = 1

Unfortunately, this fails with the following error:

The database is not published.

OK, so part of SQL Server knows it’s not being replicated, I guess that’s good. A lot of sites suggest physically removing the log file by detaching the database, renaming or deleting the log file, and reattaching the database. There’s a much simpler, gentler way:

-- publish database (this doesn't actually create
-- a snapshot--it only takes a cople seconds)
sp_replicationdboption 'yourdb','publish','true'

-- clear that replicaton marker (yourdb should be selected)
EXEC sp_repldone @xactid = NULL, @xact_seqno = NULL, @numtrans = 0, @time = 0, @reset = 1

-- unpublish database
sp_replicationdboption 'yourdb','publish','false'

Yes, you simply enable replication long enough to clear the marker. This only takes a few seconds as it doesn’t actually generate a new snapshot or anything expensive like that. Now you’re free to truncate the log!

OR

http://blog.wassupy.com/2011/03/truncating-log-of-previously-replicated.html

Truncating the log -Replication

06 July 2011

Instant File Initialization Speeds SQL Server

http://www.bradmcgehee.com/2010/07/instant-file-initialization-speeds-sql-server/

OR

Sometimes, its just the smallest of details that can make all the difference. For example, on my test system (see the end of this posting for a description), I created a new 50GB database. The database creation process took about 5 minutes and 50 seconds to complete.

Next, I populated the database with over 61 million rows of data, which virtually occupied all of the available space within the newly created database. After that, I backed up the database using SSMS, and then I deleted the original database.

At this point, I restored the database from the backup using SSMS. Below, you see the typical Restore Database screen.

At the bottom, right-hand side of the screen in the Progress box, notice the “Executing (0%)” indicator. Between the time I clicked the OK button to begin the restore, and when the “Executing (0%)” counter began to move, it took about 5 minutes and 50 seconds. At that point, the counter began to increment and the database was restored.

Now I make one very small change to my SQL Server instance (I’ll describe it in just a moment), and then I repeat the above steps (after deleting the database I just restored). First, I created a new 50GB database. This time, instead of taking 5 minutes and 50 seconds to create the database, it takes just under 2 seconds, a savings of about 5 minutes and 48 seconds. Next, I populated the database with the same amount of data as before, backed it up, and then deleted the original file. When I restored the database this time around, instead of having to wait 5 minutes and 50 seconds before the backup began to restore, I only had to wait just under 2 seconds. In both of these cases, I saved a significant amount of time.

So what was the very small change that I made, and why did it radically reduce the amount of time for database creation and database restoration to occur? I turned instant file initialization on.

What is Instant File Initialization?

In my first two examples, before instance file initialization was turned on, the reason it took so long for the database to be created, or the database to be restored (before a database can be restored, its space must first be pre-allocated, much like creating a new database), SQL Server had to go to every page in the 50 GB database and zero each one of them out. It can take a lot of time for SQL Server to go to every 8K page in a file (especially very large files) and physically zero out each page. When instant file initialization is turned on, SQL Server doesn’t have to zero out every 8K page that has been allocated. Instead, the space is just allocated to SQL Server by the operating system in one fell swoop, which is a very quick process, potentially saving you a great deal of time.

How Do You Turn Instant File Initialization On?

Unlike most configuration features in SQL Server, there is no on/off switch for instant file initialization. Instead, you have to assign a specific user right to the SQL Server Service (mssqlserver) account. Here’s what you need to do to turn on instant file initialization.

First of all, to use instant file initialization with SQL Server in a production environment, you must be using some combination of:
•Windows Server 2003 or
•Windows Server 2008 or
•Windows Server 2008 R2

and using:
•SQL Server 2005 (any edition) or
•SQL Server 2008 (any edition) or
•SQL Server 2008 R2 (any edition)

Second, you must assign the SQL Server Service (mssqlserver) a special user right called “Perform volume maintenance tasks”. To do this, start the Local Security Policy tool (you must be a local administrator to perform this task), then drill down to Security Settings | Local Policies | User Rights Assignment | Perform volume maintenance tasks, as you see in the screenshot below.

Once you have located “Perform volume maintenance tasks”, right-click on it and select “Properties”, and the “Perform volume maintenance tasks Properties” screen appears. Click on “Add User or Group” and then proceed through the remaining screens until you select the account that is being used as the service account for SQL Server. In the screen shot below, notice that I have added the BRADMCGEHEE\sqlserverservice account to this user rights assignment. This is the user account I use on my test server to run my SQL Server instance.

Once the SQL Server service account has been assigned this user right, you will have to restart the SQL Server service (of course, only when it is not being used), and from this point forward, instant file initialization is turned on for all MDF files in your SQL Server instance.

Note: If your SQL Server service account is a member of the local administrators group, then the account already has the “Perform volume maintenance tasks” user right and you don’t need to assign it again.

Why Isn’t Instant File Initialization Turned On by Default?

When a SQL Server instance is first installed, one of the things you must enter is a SQL Server service account. If you follow the best practice and select a domain user account to be used as the SQL Server service account, the setup process automatically assigns the domain user account with only just enough rights and permissions to run SQL Server. The “Perform volume maintenance tasks” user right is not automatically assigned during installation because it is not required to run SQL Server, and because allowing the service account to have this additional user right introduces a very small security risk.

Oh no, a security risk! Well, not really much of a security risk. Here’s the possible security risk scenario. The disk that is being used to create the new database on has been used for storing data that has been previously deleted. As you may know, when data is deleted from disk by the operating system, it really is not physically deleted; the space holding the data is just marked as being available. At some point, the older data will be overwritten with new data. This occurs all the time on millions of computers throughout the world every day. And as such, any data that has been marked for deletion, but not yet overwritten, is potentially available for access if you have the right tools and know what you are doing. In fact, undelete software uses this to recover data that has been accidently deleted.

When instant file initialization is not turned on, and when SQL Server allocates space for an MDF file, each of the pages allocated for the database is zeroed out, which removes the older data, in theory, preventing it from being accessed. I say “in theory” because there are computer forensics techniques that can even recover data that has been overwritten, but that discussion is really not applicable here.

So if instant file initialization is turned on, there is a very slight risk that someone could go to the pages allocated for the new database and read any older data that still may exist there. This is essentially a non-issue in virtually every organization, other than those that require very high security. But because of this potential security issue, instant file initialization is not turned on by default.

If instant file initialization is turned on, and pages are not zeroed out when the database is initially created, SQL Server will automatically overwrite any data that might have been on those pages when SQL Server needs that space.

When Is Instant File Initialization Used?

If instant file initialization is turned on, it is used in all of these cases:
•When a database is first created
•When a an existing database’s size is manually increased
•When tempdb is recreated each time SQL Server is restarted
•When autogrowth kicks in
•When backups are restored (as the space has to be pre-allocated before a restore can occur)

Instant file initialization only affects MDF and NDF files, not LDF files. In other words, transaction log files can’t take advantage of instant file initialization. This is because log files are circular in nature and must be zeroed out, as random data in transaction log pages can be problematic. In my earlier test, when I created a new 50 GB database, the MDF file was 50 GB and the log file was only 1 MB. If I had created a large log file (which is not uncommon), it would have taken awhile for the log to be created, although the MDF file would have been instantly created. This is also true when you manually increase the size of a log file, or when log file autogrowth occurs. In other words, don’t expect to have all of your databases (MDF and LDF files) created in less than 2 seconds like in my test. While the MDF will be created virtually instantly, the log file may take awhile to be created.

When I was working with SQL Server 2000 a few years back, which does not support instant file initialization, one of the things that annoyed me the most when restoring large databases was waiting for the database space to be allocated before the restore actually began. During emergency database restores, this wasted a lot of precious time, preventing me from getting the database back into production as fast as I would have preferred. If you aren’t using instant file initialization today, you are facing this same problem. That’s why I recommend all SQL Server 2005/2008 instances have instant file initialization turned on. The time saved when restoring databases is the best reason to use instant file initialization.

Check to See if Your SQL Server Instances Have Instant File Initialization Turned On

Hopefully, by now, you see the benefits of using instant file initialization. Assuming that you don’t already know if instant file initialization is turned on or off on the SQL Servers your manage, I challenge you to check and see, and if you find it turned off, turn it on and reap its many benefits.

Test Hardware
•Dell T610 Tower, with a single, 6-core CPU (Intel Xeon X5670, 2.93 Ghz, 12M Cache, HT, 1333MHz FSB); 32GB 1333MHz RAM; a PERC H700 RAID controller; two 146GB 15K SAS Drives; one dual-port HBA (to connect to the DAS); and dual network connections. Hyper-threading turned off.
•One PowerVault MD3000 DAS with two, dual-port controllers, and 15 146GB 15K SAS drives. MDF files located on RAID 10 array with 10 spindles, LDF files on RAID 10 array with 4 spindles, backup drive on a single spindle.

27 June 2011

Copying a Database from SQL Server 2005 to SQL Server 2008

Right click the Management folder to open a contextual menu as shown.

Click on Copy Database... menu item.

This opens up the Copy Database Wizard's Welcome screen. Read the info on this screen which says that you can migrate database on your SQL 2000 and SQL 2005 servers with this tool.

Click on the Next button.

This brings up the screen where you need to choose a source of your database. This source can either be SQL 2000 server or SQL 2005 server. However (oops!) the default that comes up is SQL 2008 server as shown. Click on the Browse... button which brings up the Browse for Servers window where you expand the Database Engine and highlight the SQL Express server (Junior version of SQL 2005 Server) as shown. Note that the figure is a collage of two windows and couple of clicks.

Click on the Next button. This brings up the window where you choose a destination server showing SQLExpress as the default server (oops again, they seem to have it backwards). Use the ellipsis button to add the Hodentek2HTEK2008 server to the choose the destination server window as shown. Again as this is set up with windows authentication the default is accepted.

Click on the Next button. This takes you to the Select Transfer Method window of the Copy Database Wizard where you can use either the attach / detach method, or the method that uses the SQL DMO API by making the right choice. The second method which does not stop the server is chosen here although it may be a little slower than the other method.

Click on the Next button. This opens up the Select Databases section of the copy database wizard. Here you can pick and choose what databases will be used in this migration. Here the database pubsx on the SQL Express is chosen to be copied. Note that you can also move the database. It is good practice to refresh before you move away from this screen.

Click on the Next button. This brings up the Configure Destination Database (1 of 1) window. If a database with the same name exists on the destination, you can either stop the transfer, or you can drop the existing one before transfer by choosing the appropriate radio button at the bottom of the screen as shown. The folder locations where the transferred database files will be saved to are shown here . If you want you can choose another name for this database. Here the default is accepted.

Click on the Next button. In the screen that shows up, you can pick and choose database objects, an option that is not available in manual attach / detach procedure. Similarly you can choose what logins to migrate by clicking on the ellipsis button in this window (the right hand area). You can use the >> and << buttons to add, or remove objects that needs transferring. Here the default is accepted.

Click on the Next button. This is where an "Integration Services Package" is created whose properties will be configured here. The execution logging options can be chosen here. This can be Windows events log or, a text file that can be chosen as shown.

Click on the Next button. This brings up the window for the Schedule the Package step of the wizard which needs to be configured. It can be, Run immediately or, it can be scheduled using a screen that would pop-up if that option is chosen. Here the "Run immediately" option is chosen. This is the screen where you would use the proxy account for the SQL Server Agent you created earlier. Click on the drop-down handle and choose the proxy you created earlier.

After choosing the proxy indicated, click on the Next button. This takes you to the summary of actions taken so far in the Complete the Wizard screen as shown.

Click on the Finish button in the Complete the Wizard window. This brings up the Performing Operations section of the wizard and shows the processing of the various steps and finally displays the success of the operation. In case there is an error it will stop processing and display a hyperlink, which when clicked will show the error in more detail.

Click the Close button to close the window. You may now refresh the databases node in the SQL Server Management Studio server and verify that the database has been migrated. The two figures show the before and after migration contents of the databases folder in the SQL Server Management Studio.

Before Transfer

After Transfer

In the SQL Server Agent folder you can see the job created for this migration as shown. There are two other jobs created earlier.

If you bring up the properties of this page by right clicking the job you can also see the job history.

Summary

07 June 2011

Keyword or Search for Data in a DB

CREATE PROC SearchAllTables
(
@SearchStr nvarchar(100)
)
AS
BEGIN

CREATE TABLE #Results (ColumnName nvarchar(370), ColumnValue nvarchar(3630))

SET NOCOUNT ON

DECLARE @TableName nvarchar(256), @ColumnName nvarchar(128), @SearchStr2 nvarchar(110)
SET @TableName = ''
SET @SearchStr2 = QUOTENAME('%' + @SearchStr + '%','''')

WHILE @TableName IS NOT NULL
BEGIN
SET @ColumnName = ''
SET @TableName =
(
SELECT MIN(QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME))
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE = 'BASE TABLE'
AND QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME) > @TableName
AND OBJECTPROPERTY(
OBJECT_ID(
QUOTENAME(TABLE_SCHEMA) + '.' + QUOTENAME(TABLE_NAME)
), 'IsMSShipped'
) = 0
)

WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
BEGIN
SET @ColumnName =
(
SELECT MIN(QUOTENAME(COLUMN_NAME))
FROM INFORMATION_SCHEMA.COLUMNS
WHERE TABLE_SCHEMA = PARSENAME(@TableName, 2)
AND TABLE_NAME = PARSENAME(@TableName, 1)
AND DATA_TYPE IN ('char', 'varchar', 'nchar', 'nvarchar')
AND QUOTENAME(COLUMN_NAME) > @ColumnName
)

IF @ColumnName IS NOT NULL
BEGIN
INSERT INTO #Results
EXEC
(
'SELECT ''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630)
FROM ' + @TableName + ' (NOLOCK) ' +
' WHERE ' + @ColumnName + ' LIKE ' + @SearchStr2
)
END
END
END

SELECT ColumnName, ColumnValue FROM #Results
END

--To search all columns of all tables in Pubs database for the keyword "Computer"
EXEC SearchAllTables 'Computer'
GO

Query to find Columns in a Database

SELECT t.name AS table_name,
SCHEMA_NAME(schema_id) AS schema_name,
c.name AS column_name
FROM sys.tables AS t
INNER JOIN sys.columns c ON t.OBJECT_ID = c.OBJECT_ID
WHERE c.name LIKE '%contact%'
ORDER BY schema_name, table_name;