Nothing can stop me, nothing holds me back from changing recovery mode and getting development on track…

Greetings and other salutations,

Today I found out that part of the development environment was in “Full Recovery Mode”.  This means that if someone isn’t taking log backups, their databases get huge, and it also means that the backups were much bigger than they should have been.  They don’t need point in time recovery in our development environment so we decided to move them to “Simple recovery”. This could have been a big all day job if I went through the GUI, but you know me, I found a way to script it out and thought I would share it. I am showing you how to do it on one server at a time:

Connect to your development server in the master database and run this query to see how many are in “Full Recovery”:

 SELECT name, recovery_model_desc
 FROM sys.databases
 WHERE recovery_model_desc = 'FULL'

When I ran it on one of my servers, there were 24 databases that needed to be adjusted. So I built this:

 SELECT 'ALTER DATABASE [' + name + '] SET RECOVERY SIMPLE ;'
 FROM sys.databases
 WHERE recovery_model_desc = 'Full'

Then I took the results from that query and copied it into a new window and ran it and just like that, all my databases are now in “Simple Mode” in Development. I ran the first query one more time to make sure everything updated as expected.

It is a beautiful thing. I hope this helps you clean up development too!

I can make your logs clap…

The SQL error log has this nasty habit of getting big when I am not looking.  There are only two ways to keep is at a normal size. One is to stop and start your SQL instance (Reboot, Restart, Stop and Start) and the other is to run this handy little script:


EXEC sp_cycle_errorlog;

This will end the current log and start a new one.  Why does this matter?  The SQL Error log holds information about your backups, failed logins, SQL errors, edition information and other fun stuff.  The bigger it is, the longer it will take SQL to load it into memory so that you can read it.  Usually when you need to read it, you are in trouble so the slower it is, the more stressed you will be.

What is a good size?  I usually try to get it to roll over around 10 MB.  I use a monitoring tool and when the large error log alert is triggered, I have it run sp_cycle_errorlog for me so mine always stay a healthy size.  You don’t need fancy tools to do this though.  If you know about how fast your logs grow, you can set up a SQL Agent job to run it on a schedule to keep your logs healthy.

How many logs should I keep? This is completely up to you, but since I keep my logs so small, I try to keep 15 of them.  Why so many? I do it so I can go back and see issues further back if needed. You can adjust the amount you keep by right clicking on SQL Server Logs in SSMS and selecting “Configure”

Configure SQL Error Logs

Super cool, but what about the Agent error logs? There is a script for them as well!


USE msdb;
GO
EXEC sp_cycle_agent_errorlog;

See? Healthy and Happy Logs! Your Logs will be clapping with joy.

Hello Darkness my old friend, I can talk to you again because my Availability Group is quiet…

We have a lovely Availability Group that holds A LOT of data that is broken into partitions.  We have 42 partitions and they are usually moving information around daily between them.   The index rebuilds on them were making our logs HUGE because the the Availability Group was taking too long to catch up, we tried both Synchronous and Asynchronous mode.  We would see all kinds of errors.  We were doing horrible things like auto shrinking our transaction log after the indexing finished and  ignoring alarms during the time the database was rebuilding.  We had requested more and more space from our storage team and sometimes the job wouldn’t even finish because it ran out of space.  Our first idea was to split out the index rebuilds so that we could do one partition at a time.

It looks like this:


ALTER INDEX IndexName
ON [dbo].Table
REBUILD PARTITION = 42

By splitting this out, we were able to get the job to finish, but with tons of alarms, and log growth.

Then we had a thought, maybe the server is just spinning too fast and we need to give the Availability Group time to catch up.  So we added some simple waits in between each step.


WAITFOR DELAY '00:10';

As an example this is in minutes and will wait for 10 minutes before running the next step.

 

It has now been a quiet week and we are looking forward to the Sound of Silence.

Takes as Long as it Takes SQL, Break on Me, I have a DAC…

The DAC, what is it? It is the Dedicated Administrator Console. Basically it is a way to connect to your SQL Server when all the other connections are tied up. But it takes a little bit of pre-planning so that you can use it when things go bad with your SQL Server.  Let’s enable it so you can test using it and know that it is there in the future.


EXEC sp_configure 'remote admin connections', 1;
GO
RECONFIGURE
GO

I was always afraid to use the DAC because I thought I had to use the command line and I am terrible with cmd. But did you know, you can connect to it through Management Studio? Now I can feel right at home when I trouble shoot a sick server.  To connect to a server using the DAC put “admin:” in front of the name of the server like this:

DAC

I use my elevated windows login for this point, but you can use what ever sys admin account that you have.

There are a few words of caution. You can only have one connection to your DAC on each server at a time. So don’t try to connect Object explorer to it. I have SQLPrompt and noticed that my server would send an alert on Severity Error 20 because SQL Prompt was trying to connect at the same time and was failing. Just be aware that you might get an error, but if everything is correct you can look down at the connection at the bottom of the query window and see you are connected.  If someone else is using the DAC, you won’t be able to use the connection, so it is a good idea to always close it when you are done.

Kendra Little b|t has a fantastic post for Brent Ozar Unlimited about the DAC and most importantly to me, how to tell who is connected.  This is the code that she wrote to help identify who is connected:


SELECT
CASE
WHEN ses.session_id= @@SPID THEN 'It''s me! '
ELSE '' END
+ coalesce(ses.login_name,'???') as WhosGotTheDAC,
ses.session_id,
ses.login_time,
ses.status,
ses.original_login_name
from sys.endpoints as en
join sys.dm_exec_sessions ses on
en.endpoint_id=ses.endpoint_id
where en.name='Dedicated Admin Connection'

Now when SQL Server Breaks on you, there is a tool that prevents us from shattering like glass.

If Crazy = Genius, I’m rebuilding one partition at a time!

We have had an index job that has been failing for a while.  This is one of those things you really don’t want to clean up because no one is complaining, but you know you should.  I had heard that I could rebuild one partition at a time, but where to start?  Today, I worked my way through it, so here it is so that you can do it too.

First you need to find the biggest indexes, there is a good chance those are the ones that live on partitions. I am removing Primary Keys.


SELECT i.[name] AS IndexName
,SUM(ps.[used_page_count]) * 8 AS IndexSizeKB
FROM sys.dm_db_partition_stats AS ps
INNER JOIN sys.indexes AS i ON ps.[object_id] = i.[object_id]
AND ps.[index_id] = i.[index_id]
WHERE i.name NOT LIKE 'PK%'
GROUP BY i.[name]
ORDER BY IndexSizeKB DESC

The top ones are most likely the ones you want to focus on.  Next, we need to track down the partition function.


SELECT * FROM sys.partition_functions

Next we are going to figure out which partition we want to rebuild.


SELECT sprv.value AS [Value], sprv.boundary_id AS [ID]
FROM sys.partition_functions AS spf
INNER JOIN sys.partition_range_values sprv ON sprv.function_id = spf.function_id
WHERE (spf.name = N'NameOfFunctionFromPartitionFunctions')
ORDER BY [ID] ASC

Pick the number of the partition you want to rebuild.

Next use your index name from earlier.  You will also need the table name and the partition number.


ALTER INDEX [IndexName]
ON [dbo].[TableName]
REBUILD PARTITION = 3

This will rebuild just the partition that you requested.

Strip it down and remove the bad query plan

Today I got to play with some really bad queries. But the queries weren’t necessarily bad, it was more they had bad plans. I thought I had already blogged about it and tried to find my code. Alas, it wasn’t there so let’s strip it down on how you would remove a bad query plan. I am leaving out the trouble shooting part of how to determine if it is a bad plan because so much of it “depends”.
First you have to find the bad query plan.  Get a unique line from your query and paste it in the query below.

USE master;
GO

SELECT usecounts, cacheobjtype, objtype, text, plan_handle
FROM sys.dm_exec_cached_plans
CROSS APPLY sys.dm_exec_sql_text(plan_handle)
WHERE usecounts > 1
AND TEXT LIKE '%Unique part of query%' --put the unique part of the query here.
ORDER BY usecounts DESC;

Now, copy the plan handle and paste it over the plan handle that I have listed here:

SELECT * FROM sys.dm_exec_query_plan (0x060001004DE4D526F0BEA28F05000);

If you click on the query_plan link, you can see what the plan looks like.  After you have reviewed it and determined the plan is bad then you can paste your plan handle over the one below to remove it from the proc cache.

DBCC FREEPROCCACHE (0x060001004DE4D526F0BEA28F05000)

There you have it. Best of luck with your bad plans.