Category: SQL Server 2016

Could not load assembly ‘Microsoft.SqlServer.Connectioninfo, Version=, Culture=netural, PublicKeyToken=89845dcd8080cc91’ or one Of its dependencies. The system cannot find the file specified.

Problem Statement:

When trying to migrate SQL Server 2008 R2 to SQL Server 2016, we identified an issue with the following error:

Could not load assembly ‘Microsoft.SqlServer.Connectioninfo, Version=, Culture=netural, PublicKeyToken=89845dcd8080cc91’ or one
Of its dependencies. The system cannot find the file specified.

As a knee jerk reaction, we initially thought it was an issue with SQL Server 2016 installation and need to install the Feature Pack for SQL Server 2016. Once applied the feature Pack, we again tested and found the same issue unfortunately(but really fortunate one!!!).

Analyzing further(I mean, reading the error message clearly, It is found the version 10.0.0 that represents Microsoft® SQL Server® 2008.
As we do not have SQL Server 2008 installed in the environment and the code(.NET application) has some reference to the version mentioned, this was not able to find the dlls in the specified path(C:\windows\assemblies\).

To proceed with our testing, we installed SQL Server 2008 R2 Feature pack and resumed our testing. Finally, it worked like a treat!!!

The learning is we always need to go to the facts(error message) than blindly presume things!!!

please find the below information for various version feature pack references:

Microsoft® SQL Server® 2016 Feature Pack (Version: 13.0.1601.0)
Microsoft® SQL Server® 2014 SP2 Feature Pack (Version: 12.0.5000.0)
Microsoft® SQL Server® 2014 Feature Pack (Version:
Microsoft® SQL Server® 2012 SP1 Feature Pack (Version:
Microsoft® SQL Server® 2012 Feature Pack (Version: 11.0.2100.60)
Microsoft® SQL Server® 2008 R2 SP2 Feature Pack (Version: 10.50.4000.0)
Microsoft® SQL Server® 2008 R2 SP1 Feature Pack (Version: 10.50.2500.0)
Microsoft® SQL Server® 2008 R2 Feature Pack (Version: 10.50.1600.1)
Microsoft SQL Server 2008 Service Pack 4 Feature Pack (Version: 10.0.6000.29)
Microsoft SQL Server 2008 Service Pack 3 Feature Pack (Version: 10.00.5500.00)
Microsoft SQL Server 2008 Service Pack 2 Feature Pack (Version: 10.00.4000.00)
SQL Server 2008 Service Pack 1 (Version: 10.00.2531.00)


One of my colleague was asking a follow up question on my earlier post DROP IF EXISTS – A handy feature in SQL Server 2016

Do we have something similar for Creating objects?
The good news is that we have “CREATE or ALTER” in SQL Server 2016 to address our long waiting requirement. However, this will not be available in RTM, but only from SP1 and above.

Applies to : SQL Server 2016 SP1 or later versions

Here is a small script to demonstrate the same.
SQL Script:

--Creating the procedure first time
--Altering the procedure 


Note: This can also be used for Functions, Views and Triggers objects as well.

Query Store in SQL Server 2016 – Overview

QueryStore feature in SQL Server 2016 is very helpful for any SQL Server resource to identify and troubleshoot the performance issues in SQL Server. This feature enables to store the query information along with query plan. The query execution statistics also collected associated with each query.

Applies to: SQL Server 2016 and later

Why do we need QueryStore feature or How does it help?

Yes, we do have an option to analyse the query execution before Querystore using Cachedplan in earlier versions. However, the downside is Cached plan will be saved in memory and it will not be available once SQL Server has been restarted. This was always a challenge for DBA/performance engineer to identify issues with Query execution.

QueryStore actually stores plan and other information in memory initially and as per the configuration it writes to disk.So, even SQL Server gets restarted, the information can be collected from the disk(those written in the disk).

Let us see the plan of the query to understand in detail.
In the plan we can see there are objects like – plan_persist_* (to read the data from disk) and QUERY_STORE_*_IN_MEM (to read data from memory)
*- denotes different objects like query/plan/runtime_stats etc…

To understand simply, let us look at the plan for a simple dmv: Sys.query_store_query


What do we need to configure for Querystore?


General ->
Operation Mode(Actual) – This is disabled by default to represent the Actual mode of Operation.

Operation Mode(Requested) – This is to configure the mode of Operations.
Options are OFF – to disable the QueryStore
Read Only – You can ONLY read information from QueryStore
Read Write – You can READ and WRITE information to QueryStore

Monitoring – >
Data Flush Interval(Minutes) – This is to specify how frequent the data needs to write to Disk from memory. As higher the number, there is a risk of losing data(if any restart occurs between the specified vaue), lower the number there is an overhead of writing the information to disk. Default value is 15 minutes.

Statistics Collection Interval – This is to record the information about execution statistics of queries being executed.Default is 1 hour.

Query Store Retention – >
Max ize(MB) – The maximum size in MB that can be allocated to store the information. Default value is 100. Once the size reaches out the specified value, it will NEVER write further, only read is available.

Query Store Capture Mode – This is to determine what needs to be collected.
Options are All – (default) which collects all query information
Auto – Collects only the relevant queries, filters out the insignificant queries.However, there is no external influence on identifying the significance, its completely an internal process.
None – No collection of information

Size Based Cleanup Mode – Auto – (Default if QueryStore is enabled.)This will cleanup old and least expensive queries from QueryStore as per the size specified.
Off – No automatic cleanup

Stale Query Threshold(Days) – Number days the Query information stays for. By enabling the QueryStore, the default value sets as 30 days.

Where do we get the information from QueryStore?

Microsoft has provided a good number of DMVs to get the QueryStore information.

The above DMVs provide enough information about Query execution statistics for you to troubleshoot your query performances.

How to purge the querystore information?
You can always purge the querystore information using wizard “Purge Query Data” in the Database Properties – > Query Store or by using the below T-SQL:


DROP IF EXISTS – A handy feature in SQL Server 2016

Microsoft has introduced a handy cool feature in SQL Server 2016 called DROP IF EXISTS for objects.

Applies to : SQL Server 2016 and later
This is applicable for dropping an object with existence check. In early versions, we need to write the existence condition and then drop the objects. For an example, if we need to drop a table, we would write code as follows:

Create Table dbo.ExistsCheck(Col1 int) 

--Code to check the existence and drop the object 
If exists (Select 1 From sys.tables where name='dbo.ExistsCheck') 
    Drop table dbo.ExistsCheck

Let us look at the execution plan and the statistics information for the below:


SQL Server 2016 and later version has a new way to do as follows:


/*Object_type can be anything like Table, Procedure, View, Function, Database, Trigger, Assembly(not supported in AZURE), Sequence, Index, Role, user, type, synonym, column.*/
Drop table If exists dbo.ExistsCheck

Using the above syntax, it is interested to note that no execution plan and no statistics generated as those are trivial operations.

/*It is to be noted that the column drop if exists syntax is different*/
ALTER TABLE tbl_verify DROP column IF EXISTS bbbb

/*Similar way is also applicable for dropping constraints as well*/
ALTER TABLE tbl_verify DROP Constraint IF EXISTS PK__tbl_veri__4EE7470B21966CBA

I personally feel this is a nice feature we can adopt in new development activities(caveat: only for SQL Server 2016 and later versions).

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