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• Does multiple files in SQL Server when using RAID help reduce conflicts in growth and file-locking?

  - by Dr Giles M

  I've been reading around and get the impression that if you are using RAID then using multiple SQL Server files within a filegroup won't yeild any more improvements, and the benefits are purely administrative (if you started to run out of space or wanted to partition off data into managable chunks for backups/balancing the data around your big server room). However, being a reasonably savvy software person, it's not unthinkable to hypothesise that, even for smaller databases that SQL Server will perform growth and locking operations (for writes) on a LOGICAL file basis, so even if you are using RAID, it seems to make sense to have multiple files in a file group to balance I/O, or does the time taken to reconstruct the data from distributed filegroups outweigh the benefits of reduced locking? I'm also aware that the behaviour and benefits may be different for tables/indeces/log. Is there a good site that distinguishes the benefits of multiple files when RAID is already in place?

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• When adding second processor to SQL Server, will it automatically balance the load?

  - by ddavis

  We have a SQL Server 2008 R2 (10.5) on a dedicated box with a single 2.4Ghz processor, which regularly runs at 70-80% CPU. We are going to be adding a significant number of users to the application and therefore want to add a second processor to the box (scale up). Will SQL Server automatically use the second processor to balance threads, or is there additional configuration that will need to be done? In other words, will adding the second processor drop my CPU usage to 35-40% per CPU, automatically balancing the load? Based on what I read here, it seems that it will: http://msdn.microsoft.com/en-us/library/ms181007.aspx However, I've read elsewhere that CPU performance gains can be made by assigning database tables to different filegroups, but I'm not sure we want to get that complicated at this point.

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• Create view or SP, only if the DB contains a pattern

  - by Randall Salas

  Hi all: I am working on a script, that needs to be run in many different SQL servers. Some of them, shared the same structure, in other words, they are identical, but the filegroups and the DB names are different. This is because is one per client. Anyway, I would like when running a script, If I chose the wrong DB, it should not be executed. I am trying to mantain a clean DB. here is my example, which only works for dropping a view if exists, but does not work for creating a new one. I also wonder how it would be for creating a stored procedure. Thx a lot. if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[ContentModDate]') and OBJECTPROPERTY(id, N'IsView') = 1) AND CHARINDEX('Content', DB_NAME()) 0 drop view [dbo].[ContentModDate] GO IF (CHARINDEX('Content', DB_NAME()) 0)BEGIN CREATE VIEW [dbo].[Rx_ContentModDate] AS SELECT 'Table1' AS TableName, MAX(ModDate) AS ModDate FROM Tabl1 WHERE ModDate IS NOT NULL UNION SELECT 'Table2', MAX(ModDate) AS ModDate FROM Table2 WHERE ModDate IS NOT NULL END END GO

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• Generate DROP statements for all extended properties

  - by jamiet

  This evening I have been attempting to migrate an existing on-premise database to SQL Azure using the wizard that is built-in to SQL Server Management Studio (SSMS). When I did so I received the following error: The following objects are not supported = [MS_Description] = Extended Property Evidently databases containing extended properties can not be migrated using this particular wizard so I set about removing all of the extended properties – unfortunately there were over a thousand of them so I needed a better way than simply deleting each and every one of them manually. I found a couple of resources online that went some way toward this: Drop all extended properties in a MSSQL database by Angelo Hongens Modifying and deleting extended properties by Adam Aspin Unfortunately neither provided a script that exactly suited my needs. Angelo’s covered extended properties on tables and columns however I had other objects that had extended properties on them. Adam’s looked more complete but when I ran it I got an error: Msg 468, Level 16, State 9, Line 78 Cannot resolve the collation conflict between "Latin1_General_100_CS_AS" and "Latin1_General_CI_AS" in the equal to operation. So, both great resources but I wasn’t able to use either on their own to get rid of all of my extended properties. Hence, I combined the excellent work that Angelo and Adam had provided in order to manufacture my own script which did successfully manage to generate calls to sp_dropextendedproperty for all of my extended properties. If you think you might be able to make use of such a script then feel free to download it from https://skydrive.live.com/redir.aspx?cid=550f681dad532637&resid=550F681DAD532637!16707&parid=550F681DAD532637!16706&authkey=!APxPIQCatzC7BQ8. This script will remove extended properties on tables, columns, check constraints, default constraints, views, sprocs, foreign keys, primary keys, table triggers, UDF parameters, sproc parameters, databases, schemas, database files and filegroups. If you have any object types with extended properties on them that are not in that list then consult Adam’s aforementioned article – it should prove very useful. I repeat here the message that I have placed at the top of the script: /* This script will generate calls to sp_dropextendedproperty for every extended property that exists in your database. Actually, a caveat: I don't promise that it will catch each and every extended property that exists, but I'm confident it will catch most of them! It is based on this: http://blog.hongens.nl/2010/02/25/drop-all-extended-properties-in-a-mssql-database/ by Angelo Hongens. Also had lots of help from this: http://www.sqlservercentral.com/articles/Metadata/72609/ by Adam Aspin Adam actually provides a script at that link to do something very similar but when I ran it I got an error: Msg 468, Level 16, State 9, Line 78 Cannot resolve the collation conflict between "Latin1_General_100_CS_AS" and "Latin1_General_CI_AS" in the equal to operation. So I put together this version instead. Use at your own risk. Jamie Thomson 2012-03-25 */ Hope this is useful to someone! @Jamiet

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• Maintenance window and recovery for a large database

  - by NYSystemsAnalyst

  One of our teams is developing a database that will be somewhat large (~500GB) and grow from there (I know 500 Gigs may seem small to many of you, but it will be one of the larger databases in our shop). One of the issues they are grappling with is backing up and restoring the database. Basically, the database will have several "data" tables and one table used for storing images / documents. We need to accomplish the following: Be able to quickly backup and restore only the data tables (sans images) to our test server for debugging and testing purposes. In the event of a catastrophic database failure, restore the data tables only to get most of the application up and running ASAP. Then, restore the images table when possible. Backup the database within the allotted nightly time window (a few hours). My questions are: Is it possible to accomplish the first two goals while still having the images stored in the same database? If so, would we use filegroups, filestream, or something else? How do other shops backup their databases in a reasonable time window while maintaining high availability? Do you replicate to a second server and backup from there?

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• SQL SERVER – SSMS: Memory Usage By Memory Optimized Objects Report

  - by Pinal Dave

  At conferences and at speaking engagements at the local UG, there is one question that keeps on coming which I wish were never asked. The question around, “Why is SQL Server using up all the memory and not releasing even when idle?” Well, the answer can be long and with the release of SQL Server 2014, this got even more complicated. This release of SQL Server 2014 has the option of introducing In-Memory OLTP which is completely new concept and our dependency on memory has increased multifold. In reality, nothing much changes but we have memory optimized objects (Tables and Stored Procedures) additional which are residing completely in memory and improving performance. As a DBA, it is humanly impossible to get a hang of all the innovations and the new features introduced in the next version. So today’s blog is around the report added to SSMS which gives a high level view of this new feature addition. This reports is available only from SQL Server 2014 onwards because the feature was introduced in SQL Server 2014. Earlier versions of SQL Server Management Studio would not show the report in the list. If we try to launch the report on the database which is not having In-Memory File group defined, then we would see the message in report. To demonstrate, I have created new fresh database called MemoryOptimizedDB with no special file group. Here is the query used to identify whether a database has memory-optimized file group or not. SELECT TOP(1) 1 FROM sys.filegroups FG WHERE FG.[type] = 'FX' Once we add filegroup using below command, we would see different version of report. USE [master] GO ALTER DATABASE [MemoryOptimizedDB] ADD FILEGROUP [IMO_FG] CONTAINS MEMORY_OPTIMIZED_DATA GO The report is still empty because we have not defined any Memory Optimized table in the database.  Total allocated size is shown as 0 MB. Now, let’s add the folder location into the filegroup and also created few in-memory tables. We have used the nomenclature of IMO to denote “InMemory Optimized” objects. USE [master] GO ALTER DATABASE [MemoryOptimizedDB] ADD FILE ( NAME = N'MemoryOptimizedDB_IMO', FILENAME = N'E:\Program Files\Microsoft SQL Server\MSSQL12.SQL2014\MSSQL\DATA\MemoryOptimizedDB_IMO') TO FILEGROUP [IMO_FG] GO You may have to change the path based on your SQL Server configuration. Below is the script to create the table. USE MemoryOptimizedDB GO --Drop table if it already exists. IF OBJECT_ID('dbo.SQLAuthority','U') IS NOT NULL DROP TABLE dbo.SQLAuthority GO CREATE TABLE dbo.SQLAuthority ( ID INT IDENTITY NOT NULL, Name CHAR(500)  COLLATE Latin1_General_100_BIN2 NOT NULL DEFAULT 'Pinal', CONSTRAINT PK_SQLAuthority_ID PRIMARY KEY NONCLUSTERED (ID), INDEX hash_index_sample_memoryoptimizedtable_c2 HASH (Name) WITH (BUCKET_COUNT = 131072) ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA) GO As soon as above script is executed, table and index both are created. If we run the report again, we would see something like below. Notice that table memory is zero but index is using memory. This is due to the fact that hash index needs memory to manage the buckets created. So even if table is empty, index would consume memory. More about the internals of how In-Memory indexes and tables work will be reserved for future posts. Now, use below script to populate the table with 10000 rows INSERT INTO SQLAuthority VALUES (DEFAULT) GO 10000 Here is the same report after inserting 1000 rows into our InMemory table.    There are total three sections in the whole report. Total Memory consumed by In-Memory Objects Pie chart showing memory distribution based on type of consumer – table, index and system. Details of memory usage by each table. The information about all three is taken from one single DMV, sys.dm_db_xtp_table_memory_stats This DMV contains memory usage statistics for both user and system In-Memory tables. If we query the DMV and look at data, we can easily notice that the system tables have negative object IDs.  So, to look at user table memory usage, below is the over-simplified version of query. USE MemoryOptimizedDB GO SELECT OBJECT_NAME(OBJECT_ID), * FROM sys.dm_db_xtp_table_memory_stats WHERE OBJECT_ID > 0 GO This report would help DBA to identify which in-memory object taking lot of memory which can be used as a pointer for designing solution. I am sure in future we will discuss at lengths the whole concept of In-Memory tables in detail over this blog. To read more about In-Memory OLTP, have a look at In-Memory OLTP Series at Balmukund’s Blog. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Tips and Tricks, T SQL Tagged: SQL Memory, SQL Reports

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• SQL SERVER – What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1

  - by Pinal Dave

  This is the first part of the series Incremental Statistics. Here is the index of the complete series. What is Incremental Statistics? – Performance improvements in SQL Server 2014 – Part 1 Simple Example of Incremental Statistics – Performance improvements in SQL Server 2014 – Part 2 DMV to Identify Incremental Statistics – Performance improvements in SQL Server 2014 – Part 3 Statistics are considered one of the most important aspects of SQL Server Performance Tuning. You might have often heard the phrase, with related to performance tuning. “Update Statistics before you take any other steps to tune performance”. Honestly, I have said above statement many times and many times, I have personally updated statistics before I start to do any performance tuning exercise. You may agree or disagree to the point, but there is no denial that Statistics play an extremely vital role in the performance tuning. SQL Server 2014 has a new feature called Incremental Statistics. I have been playing with this feature for quite a while and I find that very interesting. After spending some time with this feature, I decided to write about this subject over here. New in SQL Server 2014 – Incremental Statistics Well, it seems like lots of people wants to start using SQL Server 2014′s new feature of Incremetnal Statistics. However, let us understand what actually this feature does and how it can help. I will try to simplify this feature first before I start working on the demo code. Code for all versions of SQL Server Here is the code which you can execute on all versions of SQL Server and it will update the statistics of your table. The keyword which you should pay attention is WITH FULLSCAN. It will scan the entire table and build brand new statistics for you which your SQL Server Performance Tuning engine can use for better estimation of your execution plan. UPDATE STATISTICS TableName(StatisticsName) WITH FULLSCAN Who should learn about this? Why? If you are using partitions in your database, you should consider about implementing this feature. Otherwise, this feature is pretty much not applicable to you. Well, if you are using single partition and your table data is in a single place, you still have to update your statistics the same way you have been doing. If you are using multiple partitions, this may be a very useful feature for you. In most cases, users have multiple partitions because they have lots of data in their table. Each partition will have data which belongs to itself. Now it is very common that each partition are populated separately in SQL Server. Real World Example For example, if your table contains data which is related to sales, you will have plenty of entries in your table. It will be a good idea to divide the partition into multiple filegroups for example, you can divide this table into 3 semesters or 4 quarters or even 12 months. Let us assume that we have divided our table into 12 different partitions. Now for the month of January, our first partition will be populated and for the month of February our second partition will be populated. Now assume, that you have plenty of the data in your first and second partition. Now the month of March has just started and your third partition has started to populate. Due to some reason, if you want to update your statistics, what will you do? In SQL Server 2012 and earlier version You will just use the code of WITH FULLSCAN and update the entire table. That means even though you have only data in third partition you will still update the entire table. This will be VERY resource intensive process as you will be updating the statistics of the partition 1 and 2 where data has not changed at all. In SQL Server 2014 You will just update the partition of Partition 3. There is a special syntax where you can now specify which partition you want to update now. The impact of this is that it is smartly merging the new data with old statistics and update the entire statistics without doing FULLSCAN of your entire table. This has a huge impact on performance. Remember that the new feature in SQL Server 2014 does not change anything besides the capability to update a single partition. However, there is one feature which is indeed attractive. Previously, when table data were changed 20% at that time, statistics update were triggered. However, now the same threshold is applicable to a single partition. That means if your partition faces 20% data, change it will also trigger partition level statistics update which, when merged to your final statistics will give you better performance. In summary If you are not using a partition, this feature is not applicable to you. If you are using a partition, this feature can be very helpful to you. Tomorrow: We will see working code of SQL Server 2014 Incremental Statistics. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: SQL Statistics, Statistics

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• SQL SERVER – Weekly Series – Memory Lane – #031

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Find Table without Clustered Index – Find Table with no Primary Key Clustered index is very important concept for any table. They impact the performance very heavily. Here is a quick script to find tables without a clustered index. Replace TEXT with VARCHAR(MAX) – Stop using TEXT, NTEXT, IMAGE Data Types Question: “Is VARCHAR (MAX) big enough to store the TEXT field?” Answer: “Yes, VARCHAR(MAX) is big enough to accommodate TEXT field. TEXT, NTEXT and IMAGE data types of SQL Server 2000 will be deprecated in a future version of SQL Server, SQL Server 2005 provides backward compatibility to data types but it is recommended to use new data types which are VARHCAR (MAX), NVARCHAR (MAX) and VARBINARY (MAX).” Limiting Result Sets by Using TABLESAMPLE – Examples Introduced in SQL Server 2005, TABLESAMPLE allows you to extract a sampling of rows from a table in the FROM clause. The rows retrieved are random and they are are not in any order. This sampling can be based on a percentage of number of rows. You can use TABLESAMPLE when only a sampling of rows is necessary for the application instead of a full result set. User Defined Functions (UDF) Limitations UDF have its own advantage and usage but in this article we will see the limitation of UDF. Things UDF can not do and why Stored Procedure are considered as more flexible then UDFs. Stored Procedure are more flexibility then User Defined Functions(UDF). However, this blog post is a good read to know what are the limitations of UDF. Change Database Compatible Level – Backward Compatibility For a long time SQL Server stayed on the compatibility level of 80 which is of SQL Server 2000. However, as soon as SQL Server 2005 introduced the issue of compatibility was quite a major issue. Since that time MS has been releasing the versions at every 2-3 years, changing compatibility is a ever popular topic. In this blog post, we learn how we can do the same using T-SQL. We can also do the same using SSMS and here is the blog post for the same: Change Database Compatible Level – Backward Compatibility – Part 2 – Management Studio. Constraint on VARCHAR(MAX) Field To Limit It Certain Length How can I limit the VARCHAR(MAX) field with maximum length of 12500 characters only. His Question was valid as our application was allowed 12500 characters. First of all – this requirement is bit strange but if someone wants to do the same, they can do it as described in this blog post. 2008 UNPIVOT Table Example Understanding UNPIVOT can be very complicated at times. In this blog post, I have attempted to explain the same concept in very simple words. Create Default Constraint Over Table Column A simple straight to script blog post – I still use this blog quite many times for my own reference. UDF – Get the Day of the Week Function It took me 4 iteration to find this very simple function which can immediately get the day of the week in a single line. 2009 Find Hostname and Current Logged In User Name There are two tricks listed in this blog post where users can find out the hostname and current logged user name immediately and very easily. Interesting Observation of Logon Trigger On All Servers When I was doing a project, I made an interesting observation of executing a logon trigger multiple times. It was absolutely unexpected for me! As I was logging only once, naturally, I was expecting the entry only once. However, it did it multiple times on different threads – indeed an eccentric phenomenon at first sight! Difference Between Candidate Keys and Primary Key One needs to be very careful in selecting the Primary Key as an incorrect selection can adversely impact the database architect and future normalization. For a Candidate Key to qualify as a Primary Key, it should be Non-NULL and unique in any domain. I have observed quite often that Primary Keys are seldom changed. I would like to have your feedback on not changing a Primary Key. Create Multiple Filegroup For Single Database Why should one create multiple file group for any database and what are the advantages of the same. In this blog post, I explain the same in detail. List All Objects Created on All Filegroups in Database In this blog post we discuss the essential question – “How can I find which object belongs to which filegroup. Is there any way to know this?” 2010 DATE and TIME in SQL Server 2008 When DATE is converted to DATETIME it adds the of midnight. When TIME is converted to DATETIME it adds the date of 1900 and it is something one wants to consider if you are going to run scripts from SQL Server 2008 to earlier version with CONVERT. Disabled Index and Update Statistics If you do not need a nonclustered index, I suggest you to drop it as keeping them disabled is an overhead on your system. This is because every time the statistics are updated for system all the statistics for disabled indexes are also updated. Precision of SMALLDATETIME – A 1 Minute Precision The precision of the datatype SMALLDATETIME is 1 minute. It discards the seconds by rounding up or rounding down any seconds greater than zero. 2011 Getting Columns Headers without Result Data – SET FMTONLY ON SET FMTONLY ON returns only metadata to the client. It can be used to test the format of the response without actually running the query. When this setting is ON the resultset only have headers of the results but no data. Copy Database from Instance to Another Instance – Copy Paste in SQL Server SQL Server has a feature which copy database from one database to another database and it can be automated as well using SSIS. Make sure you have SQL Server Agent Turned on as this feature will create a job. Puzzle – SELECT * vs SELECT COUNT(*) If you have ever wondered SELECT * gives error when executed alone but SELECT COUNT(*) does not. Why? in that case, you should read this blog post. Creating All New Database with Full Recovery Model This blog post is very based on very interesting story where the user wants to do something by default for every single new database created. Model database is a secret weapon which should be used very carefully and with proper evalution. If used carefully this can be a very much beneficiary when we need a newly created database behave in certain fashion. 2012 In year 2012 I had two interesting series ran on the blog. If there is no fun in learning, the learning becomes a burden. For the same reason, I had decided to build a three part quiz around SEQUENCE. The quiz was to identify the next value of the sequence. I encourage all of you to take part in this fun quiz. Guess the Next Value – Puzzle 1 Guess the Next Value – Puzzle 2 Guess the Next Value – Puzzle 3 Can anyone remember their final day of schooling?  This is probably a silly question because – of course you can!  Many people mark this as the most exciting, happiest day of their life.  It marks the end of testing, the end of following rules set by teachers, and the beginning of finally being able to earn money and work in your chosen field. Read five part series on developer training subject Developer Training - Importance and Significance - Part 1 Developer Training – Employee Morals and Ethics – Part 2 Developer Training – Difficult Questions and Alternative Perspective - Part 3 Developer Training – Various Options for Developer Training – Part 4 Developer Training – A Conclusive Summary- Part 5 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SqlBulkCopy is slow, doesn't utilize full network speed

  - by Alex

  Hi, for that past couple of weeks I have been creating generic script that is able to copy databases. The goal is to be able to specify any database on some server and copy it to some other location, and it should only copy the specified content. The exact content to be copied over is specified in a configuration file. This script is going to be used on some 10 different databases and run weekly. And in the end we are copying only about 3%-20% of databases which are as large as 500GB. I have been using the SMO assemblies to achieve this. This is my first time working with SMO and it took a while to create generic way to copy the schema objects, filegroups ...etc. (Actually helped find some bad stored procs). Overall I have a working script which is lacking on performance (and at times times out) and was hoping you guys would be able to help. When executing the WriteToServer command to copy large amount of data ( 6GB) it reaches my timeout period of 1hr. Here is the core code for copying table data. The script is written in PowerShell. $query = ("SELECT * FROM $selectedTable " + $global:selectiveTables.Get_Item($selectedTable)).Trim() Write-LogOutput "Copying $selectedTable : '$query'" $cmd = New-Object Data.SqlClient.SqlCommand -argumentList $query, $source $cmd.CommandTimeout = 120; $bulkData = ([Data.SqlClient.SqlBulkCopy]$destination) $bulkData.DestinationTableName = $selectedTable; $bulkData.BulkCopyTimeout = $global:tableCopyDataTimeout # = 3600 $reader = $cmd.ExecuteReader(); $bulkData.WriteToServer($reader); # Takes forever here on large tables The source and target databases are located on different servers so I kept track of the network speed as well. The network utilization never went over 1% which was quite surprising to me. But when I just transfer some large files between the servers, the network utilization spikes up to 10%. I have tried setting the $bulkData.BatchSize to 5000 but nothing really changed. Increasing the BulkCopyTimeout to an even greater amount would only solve the timeout. I really would like to know why the network is not being used fully. Anyone else had this problem? Any suggestions on networking or bulk copy will be appreciated. And please let me know if you need more information. Thanks. UPDATE I have tweaked several options that increase the performance of SqlBulkCopy, such as setting the transaction logging to simple and providing a table lock to SqlBulkCopy instead of the default row lock. Also some tables are better optimized for certain batch sizes. Overall, the duration of the copy was decreased by some 15%. And what we will do is execute the copy of each database simultaneously on different servers. But I am still having a timeout issue when copying one of the databases. When copying one of the larger databases, there is a table for which I consistently get the following exception: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. It is thrown about 16 after it starts copying the table which is no where near my BulkCopyTimeout. Even though I get the exception that table is fully copied in the end. Also, if I truncate that table and restart my process for that table only, the tables is copied over without any issues. But going through the process of copying that entire database fails always for that one table. I have tried executing the entire process and reseting the connection before copying that faulty table, but it still errored out. My SqlBulkCopy and Reader are closed after each table. Any suggestions as to what else could be causing the script to fail at the point each time?

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