SQL Server with Mr. Denny


May 11, 2009  11:00 AM

How do I change from push to pull subscriptions in SQL Replication?

Denny Cherry Denny Cherry Profile: Denny Cherry

The official answer is to delete the subscriber and recreate it pushing a new snapshot to the subscriber.

The much quicker and easier method is as follows.

1. Stop the distribution agent on the machine that it’s currently running on.

2. Disable the SQL Agent job that runs the distribution agent.

3. Script out the SQL Agent job from the old server and create it on the new server.

4. Enable the job on the new server.

Done.  You have just changes replication from being a push to a pull (or from being a pull to a push).

If you wanted to you could even setup your distribution agent on a third computer, but it is easier to keep track of everything if it’s running on the distributor or the subscriber.

Happy replicating.

Denny

May 7, 2009  11:00 AM

Pull vs. Push Subscriptions? Which one should you use?

Denny Cherry Denny Cherry Profile: Denny Cherry

This is a “it depends” sort of question.

These are my recommendations, your mileage may vary.

Your distributor is on the same system as your publisher – Pull is probably for you

Your Subscribers are a very high transaction count – Push is probably for you

You need to manually copy the subscription over the network to the subscriber and load it up from the local drive – Pull is probably for you

Your distributor is on a separate from the publisher – Push is probably for you

The distributor is on the same server as your subscriber – Either, as the agent will be running on the distributor either way

You have a slow network link – Either, slow networks aren’t overcome with either technique

If you have specific’s you’d like to ask about, post your questions below, or in the ITKE forum.

Denny


May 4, 2009  11:00 AM

How can I remove duplicate records in my tables?

Denny Cherry Denny Cherry Profile: Denny Cherry

All to often we end up with duplicate rows in a table.  The best way to keep duplicate rows out of the database is to not let them in.  But assume that they are there.  This bit of sample code shows how to delete those duplicate rows quickly and easily in a single statement.  No temp tables required (I use a temp table to put the data into for example purposes).  This code is for SQL 2005 and up as it uses some features which were introduced in SQL Server 2005.  SQL Server 2000 would require a totally different technique.

CREATE TABLE #DuplicateRows /*Create a new table*/
(Col1 INT,
Col2 INT,
Col3 INT)

INSERT INTO #DuplicateRows /*Load up duplicate rows*/
SELECT 1,1,1
UNION ALL
SELECT 1,1,1
UNION ALL
SELECT 1,1,1
UNION ALL
SELECT 2,2,2
UNION ALL
SELECT 2,2,2
UNION ALL
SELECT 2,2,2

SELECT *
FROM #DuplicateRows; /*Check that the data is actually hosed*/

WITH Cleaning AS (SELECT ROW_NUMBER() OVER(ORDER BY Col1, Col2, Col3) as row,
Col1,
Col2,
Col3
FROM #DuplicateRows)

DELETE FROM Cleaning /*Delete the rows which are duplicates*/
WHERE Row NOT IN (SELECT row FROM  (SELECT Col1, Col2, Col3, MIN(row) row
FROM Cleaning a
GROUP BY Col1, Col2, Col3) b)

SELECT * /*Check the table to see that it is clean*/
FROM #DuplicateRows

DROP TABLE #DuplicateRows /*Clean up the table*/

Hopefully you find this code useful.

Denny


May 1, 2009  5:03 AM

Should I install an Anti-Virus software on my server?

Denny Cherry Denny Cherry Profile: Denny Cherry

Yes, for crying out loud yes.

Every server that can access the Internet or be access from the Internet, or that can be accessed from a computer that can access the Internet should have an anti-virus on it.  Preferably a corporate wide solution like Trend Micro, McAfee, Norton, etc. so that the server reports back to a central server to make it easier to find out if a machine has a problem.

Next comes what should be scanned.  I prefer to exclude the mdf, ndf, and ldf files.  I don’t like to exclude the entire folder as this creates a hiding place where a virus could stick infected files.  If possible have it exclude the mdf, ndf and ldf files from old the correct folders only.  Even if a virus scanner wanted to scan the database files it wouldn’t be able to as the files are locked open by the SQL Server so that nothing else can access them.  By not excluding the files all you are doing is throwing alerts to the monitoring server that files couldn’t be scanned.

Odds are a full scan doesn’t need to be done against the server all that often as the files on the hard drive of the server aren’t going to change all that often.  Any virus that comes in from the network should be caught by the real time engine that is running at the time.  You will want to do a full scan every once and a while (every couple of weeks or so) incase something came in over the network was saved and setup to launch at the next reboot but wasn’t yet in the virus definition file.

Denny


April 28, 2009  4:51 AM

Why should the DBA care about Network Firewalls?

Denny Cherry Denny Cherry Profile: Denny Cherry

All to often I see people online asking some sort of question about connecting to their CoLo’ed SQL Server and they connect directly over the Internet.  This is nuts people.  If you can access your SQL Server via Management Studio from anywhere on the Internet so can people who would love to break into your SQL Server and use the machine for their own uses.

SQL Servers shouldn’t every be directly accessible from the Internet.  Even if you have to use public IPs to host the machines, make sure that there is a firewall setup between that server and the public Internet so that no one has any sort of direct access to the machine from outside of the data center.

How do you manage the SQL Server in this case?  You use the router’s built in functions to setup a point to point VPN with your office router so that you can securely communicate with the servers in the CoLo without sending that data in plain text over the Internet.

For that matter while you are locking down the SQL Server, suggest that the Web Servers be locked down as well.  The only ports that they should have open are 80 and 443 unless you are running streaming servers, or known FTP servers.

If your servers have been sitting exposed on the public Internet then I highly suggest that you install an Anti-virus on them and check for Viruses, malware, etc that’s doing stuff you don’t want it to be doing.

Several years ago I was doing some work for a company that had Windows 2003 servers sitting directly on the Internet without an Anti-Virus and with no firewall.  When I got to the machines and took them off the Internet for cleaning there were over 200 viruses on the machines that they had no idea were on there.  There complaint was that the machines were running slow, and network costs kept going up.  God only knows what sort of network traffic these viruses were generating as they did what ever it was they were trying to do.

Denny


April 26, 2009  5:29 AM

SQL Server Standard Edition getting Lock Pages in Memory

Denny Cherry Denny Cherry Profile: Denny Cherry

Microsoft SQL Server 2005 and 2008 Standard edition will be getting the Lock Pages in Memory feature that SQL Server Enterprise Edition has had starting in SQL Server 2005.  This was announced by Bob Ward via the CSS Blog in his post “SQL Server, Locked Pages, and Standard SKU…“.  Per Bob’s post a CU will be released for SQL 2005 SP3 and SQL 2008 SP1 which will allow for a trace flag to be used to turn this feature on.

On behalf of the users I’d like to thank Bob and the rest of the SQL Server team for being able to get this into the product.

On behalf of the developer team, I emplore you to not turn this on for no reason.  Only use this feature once you understand what this feature does and in the correct places.

The Locked Pages flag bascially tells the SQL Server that if it is told to flush RAM to disk to ignore it.  If the setting is enabled then SQL doesn’t flush to disk.  If you find that your SQL Server is flushing to disk, don’t just enable the flag and move on.  I emplore you to contact CSS and figure out why SQL is being told to flush to disk.  This is the only way the bug will be fixed.  Once the issue has been reported to Microsoft and they have the information they need enable the flag until the bug is fixed.  Then install the patch to fix the bug, disable the flag and you’ll be fine.

Because of the fact that this is how bugs are found and fixed I hope that this is a CSS only CU which will require that users contact CSS before they can get the fix.

Denny


April 23, 2009  11:00 AM

New SQL Server 2008 MCTS Certification Book

Denny Cherry Denny Cherry Profile: Denny Cherry

There’s a new SQL Server 2008 MCTS Certification book on the market.  It is “The Real MCTS SQL Server 2008 Exam 70-432 Database Implementation and Maintenance“.  I normally don’t post book releases as there are a lot of new books coming out these days.  However I published this one because I wrote part of it.  The book is a complitation of several authers work, and I wrote three of the chapters in the book.

So if you are looking to get your MCTS Certification I’d recommend that you check it out.

This is my first book credit (though not listed on Amazon), and there will be a second one from the same publisher coming out soon.

Denny


April 20, 2009  11:00 AM

Yes DBAs you really do have to deal with licensing

Denny Cherry Denny Cherry Profile: Denny Cherry
SQL Server, SQL Server 2000, SQL Server 2005, SQL Server 2008, SQL Server 2008 R2, SQL Server 2012, SQL Server 2014, SQL Server licensing

Probably one of the least fun things about being a DBA is having to deal with the licensing of SQL Server. Continued »


April 16, 2009  11:00 AM

Setting up Visual Studio 2005 to use more than 2 Gigs of RAM

Denny Cherry Denny Cherry Profile: Denny Cherry

One of my developers came to me asking me to add more RAM to the c++ build server.  However the machine was already at 2 Gigs so I wasn’t sure if adding more RAM wouldn’t help.  Turns out that VS 2005 doesn’t support AWE so adding more RAM wasn’t going to be of much help.  Until I found a post by Steve Harman entitled Hacking Visual Studio to Use More Than 2Gigabytes of Memory.

After making those changes it seamed to work.

Denny


April 13, 2009  11:00 AM

Datacenter Migration In Progress

Denny Cherry Denny Cherry Profile: Denny Cherry

For those of you who know me, or have heard me talk at a Code Camp in the last year, you’ve heard me talk about a data center migration that I want to do from Rackspace in Texas to our own equipment in the LA area.  Well that day has finely come.

Our current environment has served us well, but we have outgrown the services that Rackspace can offer us, and we have purchased our own production environment.  This isn’t any rinky dink environment either.  We are starting out with a fully redundant, highly available environment which can be scaled by simply deploying more VMs, and in the event that the VMware hardware is over tasked by simply plugging another VMware server into the mix, and shifting the VMs from one node of the cluster to another.

We are very proud of our new environment, so I figured that I’d give you some of the tech specs of it (yeah, I’m totally bragging here).

On the storage side of things we’ve got an EMC CX4-240 with ~35TB of storage laid out in three tiers.  This is connected via multiple 4 Gig fibre cables to a pair of Cisco fibre switches.  Each fibre switch is connected to each of the SAN attached servers.

We went with Dell servers (I would have preferred HP servers, but I was overruled).

The SQL Servers and the VMware servers are identical.  Quad chip, quad core servers each with 64 Gigs of RAM.  Each pair will be clustered for High Availability.  The VMware servers will look a little like they puked cables out of the back.  Because of all the various subnets and to ensure that each subnet is connected to each of the redundant network switches each of the VMware ESX servers will have 11 Ethernet cables, and 2 fibre cables coming out of the back.

The VMware vCenter services are running on a little single chip quad core server.  This is the only part of the system which isn’t redundant, but ESX can run fine for up to 14 days without the License server running, and since this machine has a 4 hour turn around on parts we’ll be fine if the machine dies.

The file servers which host the screenshots, emails, etc which have been captured by our application and will be served to the website upon request are a pair of dual chip, quad core servers also clustered for high availability.

All the servers are SAN attached via the fibre and all data will be saved on the SAN.

Our current environment is much smaller.  A single SQL Server, three web servers, and two file servers.  The only redundant pieces are the fibre cables from the SQL Server to the SAN, and the fact that we have three web servers.  However if the newer web server goes out in the middle of the day, the other two will choke at this point.

Rackspace has been pretty good to us over the years.  It just wasn’t cost effective for us to purchase this level of hardware before now, and Rackspace was able to provide us with a good service level for a reasonable price.  But at this point, because of the amount of hardware we were looking to move into, and the amount of bandwidth we are going to be using it simply became more cost effective for us to host the systems at a local CoLo.

The main reason that I’m telling everyone this is that if you have been trying to find me for the last two weeks or so this is why I can’t be found.  I’ve been spending pretty much every waking moment this together and getting it all setup so that we can migrate over to it.

Needless to say its an awesome project.  How many people get the chance to build a new data center and design it the way they want to from scratch.  Pretty much no one.  Data centers usually grow from a small config of a server or two in a sporadic way, and they are inherited from one person to the next.  But this time I get to design everything they way I want to from the grown up.  It’s going to be a blast.

Denny


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