Archive for March, 2017

Interesting one today:

On one of our production machines, we recently added a new LUN to a SQL cluster. A task like this is a team effort. Sysadmins perform some steps and DBA carry out the remaining. In this article, the main focus is on covering the steps after the LUN is added to the OS & Sql Cluster by the sysadmins.  For context, we’ll start with high level steps before going into details.

Sysadmins steps

  1. Add new storage to the machine/OS as an available storage
  2. Format the available drive with appropriate settings (cluster size) and add it as a new drive
  3. Make drive available to the Cluster using “Add Disk” screen in FailOver Cluster Management tool.

DBAs steps

  1. Add available storage to Sql Cluster
  2. Configure dependency (and check the report before & after)
  3. Add data file on the new cluster storage drive

Here we’ll cover the DBA steps in detail:

Some of these steps were covered under a different recent article as part of dealing with an error message, but here we’ll cover it as a task by itself (which it is).

Add New Storage

Once sysadmins have made the new storage as an ‘available storage’ to OS Cluster, it needs to be added as a new storage location to the SQL Cluster.

In FailOver cluster manager, go to Sql Server Resource Group for this SQL Cluster and right click for detailed options and choose “Add Storage” (see image below)


Once successful, go to Storage\Disks under in FailOver Cluster Manager to confirm the availability. See image below:


Configure Dependency

Adding the storage is an important step, and equally important step is adding the new drive to Sql Cluster Dependency Chain. Dependency Chain informs Sql Sever “how to act”, when any resource in the Cluster becomes unavailable. Some resources automatically trigger cluster failover to other node; some resources do not. This decision is made based on the configurations in Dependency Chain.


Critical: Data drive/LUN that has database files is critical for optimal availability of the Sql Cluster. So, if it becomes unavailable, failing over to other available nodes is imperative to keep the cluster available.

Non-Critical: In some scenarios, Sql Server Agent is not considered as Critical. So if it stops for some reason, Cluster will make multiple attempts to start it on the same node, but may not necessarily cause failover.

This is a business decision. All these “response actions” will be configured in Cluster settings.

Now, check the dependency report (before); We can see that new drive exists in Cluster, but is not yet added to the Dependency Chain.


To Configure Dependency Chain, go to the Sql Server Resource Group under Roles in FailOver Cluster Manager. See the image below for clarity:

Then go to the bottom section for this Resource Group, where all the individual resources that are part of this Resource Group are displayed.

Under “Other Resources“, right click on Sql Server Resource and choose properties.

do As show


In the “Sql Server Properties” window, we can see the existing resources already added to dependency chain logic.


Now, go to the end of the logic list and choose “AND” for condition and pick the new Cluster Storage to be included. See image below for clarity:


After saving the settings, regenerate the Dependency Chain report. Now, we’ll see the new drive as part of the logic.


Add Database Data File to New Cluster Storage

Now, that the new drive is ready, we could easily add a new data file to the new location.

-- Add data file to new storage location
USE [master]
		  NAME 			= 	N'SampleDB_Data3'
		, FILENAME 		= 	N'U:\MSSQL\Data\SampleDB_Data3.NDF'
		, SIZE 			= 	3500 GB
		, FILEGROWTH 	= 	100 GB
		, MAXSIZE 		= 	3900 GB
Hope this helps,

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Quick one today:

Edit: Update on April 10th – Added some comments to repeat some steps, as needed

Earlier today, we ran into this error in our lab environment with replication. Two different errors, on the same environment, due to similar sequence of events.

Msg 20584, Level 16, State 1, Procedure sp_MSrepl_check_server, Line 67
Cannot drop server because it is used as a Subscriber to remote Publisher in replication.

Cannot drop server because it is used as a distributor in replication

This type of errors are rare, but one of these three options below might provide some relief.

  1. Reset Dist flag
  2. Force drop distributor
  3. Manually remove Publishers (from Distributor properties)
    1. Invalid object name ‘dbo.MSmerge_agents’

Also, see the notes in the bottom section (points to keep in mind)

Reset Dist Flag for Distributor Instance

Sometimes, the dist flag for Distributor stays set, when not supposed to. So manually resetting it helps.

--  Reset Distributor flag
EXEC master.dbo.sp_ServerOption   @server = 'REPLDist'
				, @OptName = 'dist'
				, @OptValue = 'false'

Force Drop Distributor

One of the last options is to ‘force’ drop distributor. This allows removing distributor database without running through the proper checks. This step is a high risk, high reward option; Since all checks were previously performed and all components of replication are removed, except distributor, this step might provide relief.

EXEC sp_dropdistributor @no_checks = 1, @ignore_distributor = 1

Manually Remove Publishers

Usually, the above two steps will resolve the issue. But in rare occasions, the issue persists, like in our lab. For those stubborn situation, this technique has given some relief.

Go to Replication >> Distributor Properties >> Go to Publishers (tab)

Now, un-check each Publisher and save. Important to note that, this needs to be done for one publisher at a time.


3.1 Invalid object name MSmerge_agents

In Step 3, sometimes we might run into an error like this:

Invalid object name 'dbo.MSmerge_agents'.

Not sure what the root cause is, but this seems to help:

  1. Create two tables in Distributor database
  2. Rerun Step 3

1. Create two tables in Distributor database

NOTE: This step is not necessary in all situation. So, proceed with caution.

Looks like these two tables are missing in Distribution database. Create them in the Distribution database. And then go back to Step 3 again. Or Step 3 & 2, as needed.

Note: There is no harm in adding these two tables because, after you create these tables and then successfully drop replication (including the distributor database) the new objects will be removed along with the Distributor database.

So you have a clear system at the end.

create table msmerge_agents(
	  id						INT
	, name						NVARCHAR(100)
	, publisher_id				SMALLINT
	, publisher_db				SYSNAME
	, publication				SYSNAME
	, subscriber_id				SMALLINT
	, subscriber_db				SYSNAME
	, local_job					BIT
	, job_id					BINARY(16)
	, profile_id				INT
	, anonymous_subid			UNIQUEIDENTIFIER
	, subscriber_name			SYSNAME
	, creation_date				DATETIME
	, offload_enabled			BIT
	, offload_server			SYSNAME
	, sid						VARBINARY(85)
	, subscriber_security_mode	SMALLINT
	, subscriber_password		NVARCHAR(524)
	, publisher_login			SYSNAME
	, publisher_password		NVARCHAR(524)
	, job_step_uid				UNIQUEIDENTIFIER

CREATE table MSmerge_subscriptions(
	  publisher_id		SMALLINT
	, publisher_db		SYSNAME
	, publication_id	INT
	, subscriber_id		SMALLINT
	, subscriber_db		SYSNAME
	, subscription_type INT
	, sync_type			TINYINT
	, status			TINYINT
	, subscription_time DATETIME

Points to keep in mind:

Sometimes, just the one of these steps might be enough to resolve the issue; Sometimes, it might take two of the steps. In our lab, we ended up needing all the 3 steps. the first step is easy to implement.
The second and third steps might need repeated attempts. Something like:
  1. Try Step 2, if it fails,
    1. then try step 3;
    2. If it fails, try Step 3.1
    3. If that succeeds, then go back to Step 2.
  2. Once Step 2 is successful, the distributor is fully cleared and cleaned.
Hope this helps,

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Quick one today:

Given the usage of UNPIVOT is not that common as PIVOT (which itsel is more uncommon than other techniques in TSQL), the occurance of this error is even more remote. Luckly, we ran into it earlier:

Msg 8167, Level 16, State 1, Line 5
The type of column conflicts with the type of other columns specified in the UNPIVOT list.

Following is the UNPIVOT statement that threw the error. As you can see, on the surface, everything looks correct.

--	UNPIVOT syntax that throws error
SELECT ID, Metrics, Measures
	SELECT	  Daily_Health_Check_ID
			, Environment
			, DataCenter
	FROM SampleTable
	) AS Source
	Measures FOR Metrics IN (Environment, DataCenter)

Now let’s change the datatype and size of all the columns to match.

--	After converting all colums to the same datatype & size
SELECT ID, Metrics, Measures
	SELECT	  Daily_Health_Check_ID
			, CONVERT(VARCHAR(20), Environment) AS [Environment]
			, CONVERT(VARCHAR(20), DataCenter) AS [DataCenter]
	FROM SampleTable
	) AS Source
	Measures FOR Metrics IN (Environment, DataCenter)

Voilà !! The key is to have uniformed data type & size of all columns in the source data set

Hope this helps,

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