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  • IIS 7 Application Pools using a different amount of memory on multiple servers behind a load balancer

    - by Jim March
    We have 6 servers in a web farm behind an F5. There are approximately 25 AppPools on each of these servers. On servers 1 - 5 the apppools are consuming approx 500MB Private Bytes, and 5GB Virtual Bytes. On server 6 the apppools are consuming approx 800MB Private Bytes, and 8GB Virtual Bytes. I can not seem to figure out why we have this difference. The code is the exact same on each box. We replicate the apphost.config between the boxes, so the Appplication Configs are identical. The only difference seems to be that this box consumes more RAM, and in turn ends up using a lot more CPU. During Black Friday we observed the CPU on server 6 spiking to 100% and noticed that the % Memory Commit was also near 100%, while the rest of the farm was at closer to 50% utilization. Pulling the 6th server from the load balancer dropped CPU/Memory on the 6th server back to normal, and did not cause a noticeable strain on the other servers.

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  • Hyper-v dynamic memory client machines always use maximum memory

    - by Eric P
    When I create a virtual machine in Hyper-V and set it up to use dynamic memory, the virtual machine will always use the maximum memory within the virtualized OS. Hyper-V will show the assigned memory at 514mb, but when I log into the server and pull up task manager, it will show 90% memory used. When I bump the maximum memory up to 4gb, I get the same result: 90% memory usage. Nothing is even running on the virtual machine other than a clean instal of Windows Server 2008 R2. I have also tried it with Windows 7 with the same results. Is this the expected behavior or is something setup wrong

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  • About memory cache of Linux

    - by cheneydeng
    I'm running a python script to do some statistics and the actually memory which used is low,about 10%.And no other process cost more memory.However,when i use free -m and it shows that almost 95% memory has been used.The point is that my script should do a lot of read from files,so i wonder if there's any mechanism of Linux memory cache that caused the problem?echo 1 >> /proc/sys/vm/drop_caches works,but it seems manually.How can i reduce the memory cost and doesn't make a bad effect on reading files?

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  • Debian Squeeze and available memory (1GB absent)

    - by user66279
    Hi, here I've a dedicated server with 12GB RAM and running Debian Lenny x64. dmesg | grep Memory [ 0.004000] Memory: 11917152k/12259740k available (2279k kernel code, 333820k reserved, 1022k data, 216k init) Since some days, I've another dedicated server (nearly same hardware), but with Debian Squeeze x64 (installed via debootstrap, Kernel 2.6.32-5-xen-amd64) dmesg | grep Memory [ 1.551510] Memory: 6864620k/8151916k available (3146k kernel code, 1057736k absent, 229560k reserved, 1901k data, 600k init) what does absent memory mean? And how can I get 1GB of RAM back?

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  • iPhone file corruption

    - by sfider
    Is it possible (on iPhone/iPod Touch) for a file written like this: if (FILE* file = fopen(filename, "wb")) { fwrite(buf, buf_size, 1, file); fclose(file); } to get corrupted, e.g. when app is forced to terminate? From what I know fwrite should be an atomic operation, so when I write whole file with one instruction no corruption should occure. I could not find any information on the net that would say otherwise.

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  • SQL SERVER – Weekly Series – Memory Lane – #033

    - 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 Spatial Database Definition and Research Documents Here is the definition from Wikipedia about spatial database : A spatial database is a database that is optimized to store and query data related to objects in space, including points, lines and polygons. While typical databases can understand various numeric and character types of data, additional functionality needs to be added for databases to process spatial data types. Select Only Date Part From DateTime – Best Practice A very common question which I receive is how to only get Date or Time part from datetime value. In this blog post I explain the same in very simple words. T-SQL Paging Query Technique Comparison (OVER and ROW_NUMBER()) – CTE vs. Derived Table I have received few emails and comments about my post SQL SERVER – T-SQL Paging Query Technique Comparison – SQL 2000 vs SQL 2005. The main question was is this can be done using CTE? Absolutely! What about Performance? It is identical! Please refer above mentioned article for the history of paging. SQL SERVER – Cannot resolve collation conflict for equal to operation One of the very first error I ever encountered in my career was to resolve this conflict. I have blogged about it and I have realized that many others like me who are facing this error. LEN and DATALENGTH of NULL Simple Example Here is the question for you what is the LEN of NULL value? Well it is very easy – just read the blog. Recovery Models and Selection Very simple and easy explanation of the Database Backup Recovery Model and how to select the best option for you. Explanation SQL SERVER Hash Join Hash join gives best performance when two more join tables are joined and at-least one of them have no index or is not sorted. It is also expected that smaller of the either of table can be read in memory completely (though not necessary). Easy Sequence of SELECT FROM JOIN WHERE GROUP BY HAVING ORDER BY SELECT yourcolumns FROM tablenames JOIN tablenames WHERE condition GROUP BY yourcolumns HAVING aggregatecolumn condition ORDER BY yourcolumns NorthWind Database or AdventureWorks Database – Samples Databases In this blog post we learn how to install Northwind database. I also shared the source where one can download this database as that is used in many examples on MSDN help files. sp_HelpText for sp_HelpText – Puzzle A simple quick puzzle – do you know the answer of it? If not, go ahead and read the blog. 2008 SQL SERVER – 2008 – Step By Step Installation Guide With Images When SQL Server 2008 was newly introduced lots of people had no clue how to install SQL Server 2008 and the amount of the question which I used to receive were so much. I wrote this blog post with the spirit that this will help all the newbies to install SQL Server 2008 with the help of images. Still today this blog post has been bible for all of the people who are confused with SQL Server installation. Inline Variable Assignment I loved this feature. I have always wanted this feature to be present in SQL Server. The last time when I met developers from Microsoft SQL Server, I had talked about this feature. I think this feature saves some time but make the code more readable. Introduction to Policy Management – Enforcing Rules on SQL Server If our company policy is to create all the Stored Procedure with prefix ‘usp’ that developers should be just prevented to create Stored Procedure with any other prefix. Let us see a small tutorial how to create conditions and policy which will prevent any future SP to be created with any other prefix. 2009 Performance Counters from System Views – By Kevin Mckenna Many of you are not aware of this fact that access to performance information is readily available in SQL Server and that too without querying performance counters using a custom application or via perfmon. Till now, this fact has remained undisclosed but through this post I would like to explain you can easily access SQL Server performance counter information. Without putting much effort you will come across the system viewsys.dm_os_performance_counters. As the name suggests, this provides you easy access to the SQL Server performance counter information that is passed on to perfmon, but you can get at it via tsql. Customize Toolbar – Remove Debug Button from Toolbar I was fond of SQL Server Debugger feature in SQL Server 2000. To my utter disappointment, this feature was withdrawn from SQL Server 2005. The button of the debugger is similar to a play button and is used to run debugging commands of Visual Studio. Because of this reason, it gets very much infuriating for developers when they are developing on both – Visual Studio and SSMS. Let us now see how we can remove debugging button from SQL Server Management Studio. Effect of Normalization on Index and Performance A very interesting conversation which started from twitter. If you want to read one link this is the link I encourage you to read it. SSMS Feature – Multi-server Queries Using SQL Server Management Studio (SSMS) DBAs can now query multiple servers from one window. It is quite common for DBAs with large amount of servers to maintain and gather information from multiple SQL Servers and create report. This feature is a blessing for the DBAs, as they can now assemble all the information instantaneously without going anywhere. Query Optimizer Hint ROBUST PLAN – Question to You “ROBUST PLAN” is a kind of query hint which works quite differently than other hints. It does not improve join or force any indexes to use; it just makes sure that a query does not crash due to over the limit size of row. Let me elaborate upon it in the blog post. 2010 Do you really know the difference between various date functions available in SQL Server 2012? Here is a three part story where we explored the same with examples: Fastest Way to Restore the Database Difference Between DATETIME and DATETIME2 Difference Between DATETIME and DATETIME2 – WITH GETDATE Shrinking NDF and MDF Files – Readers’ Opinion Shrinking Database always creates performance degradation and increases fragmentation in the database. I suggest that you keep that in mind before you start reading the following comment. If you are going to say Shrinking Database is bad and evil, here I am saying it first and loud. Now, the comment of Imran is written while keeping in mind only the process showing how the Shrinking Database Operation works. Imran has already explained his understanding and requests further explanation. I have removed the Best Practices section from Imran’s comments, as there are a few corrections. 2011 Solution – Puzzle – SELECT * vs SELECT COUNT(*) This is very interesting question and I am very confident that not every one knows the answer to this question. Let me ask you again – Which will be faster SELECT* or SELECT COUNT (*) or do you think this is apples and oranges comparison. 2012 Service Broker and CAP_CPU_PERCENT – Limiting SQL Server Instances to CPU Usage In SQL Server 2012 there are a few enhancements with regards to SQL Server Resource Governor. One of the enhancement is how the resources are allocated. Let me explain you with examples. Let us understand the entire discussion with the help of three different examples. Finding Size of a Columnstore Index Using DMVs One of the very common question I often see is need of the list of columnstore index along with their size and corresponding table name. I quickly re-wrote a script using DMVs sys.indexes and sys.dm_db_partition_stats. This script gives the size of the columnstore index on disk only. I am sure there will be advanced script to retrieve details related to components associated with the columnstore index. However, I believe following script is sufficient to start getting an idea of columnstore index size. Developer Training Resources and Summary Roundup Developer Training - Importance and Significance - Part 1 In this part we discussed the importance of training in the real world. The most important and valuable resource any company is its employee. Employees who have been well-trained will be better at their jobs and produce a better product.  An employee who is well trained obviously knows more about their job and all the technical aspects. I have a very high opinion about training employees and it is the most important task. Developer Training – Employee Morals and Ethics – Part 2 In this part we discussed the most crucial components of training. Often employees are expecting the company to pay for their training and the company expresses no interest in training the employee. Quite often training expenses are the real issue for both the employee and employer. Developer Training – Difficult Questions and Alternative Perspective - Part 3 This part was the most difficult to write as I tried to address a few difficult questions and answers. Training is such a sensitive issue that many developers when not receiving chance for training think about leaving the organization. Developer Training – Various Options for Developer Training – Part 4 In this part I tried to explore a few methods and options for training. The generic feedback I received on this blog post was short and I should have explored each of the subject of the training in details. I believe there are two big buckets of training 1) Instructor Lead Training and 2) Self Lead Training. Developer Training – A Conclusive Summary- Part 5 There is no better motivation than a personal desire to learn new technology. Honestly there is nothing more personal learning. That “change is the only constant” and “adapt & overcome” are the essential lessons of life. One cannot stop the learning and resist the change. In the IT industry “ego of knowing all” and the “resistance to change” are the most challenging issues. A Quick Look at Logging and Ideas around Logging Question: What is the first thing comes to your mind when you hear the word “Logging”? Strange enough I got a different answer every single time. Let me just list what answer I got from my friends. Let us go over them one by one. Beginning Performance Tuning with SQL Server Execution Plan Solution of Puzzle – Swap Value of Column Without Case Statement Earlier this week I asked a question where I asked how to Swap Values of the column without using CASE Statement. Read here: SQL SERVER – A Puzzle – Swap Value of Column Without Case Statement. I have proposed 3 different solutions in the blog posts itself. I had requested the help of the community to come up with alternate solutions and honestly I am stunned and amazed by the qualified entries. 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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  • What is the effect of running an application with "Unlimited Stack" size

    - by NSA
    Hello All, I have inherited some code that I need to maintain that can be less than stable at times. The previous people are no longer available to query as to why they ran the application in an environment with unlimited stack set, I am curious what the effects of this could be? The application seems to have some unpredictable memory bugs that we cannot find and running the application under valgrind is not an option because it slows the application down so much that we cannot actually run it. So any thoughts on what the effects of this might be are appreciated. Thank you.

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  • SQL SERVER – Weekly Series – Memory Lane – #005

    - by pinaldave
    Here is the list of curetted 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. 2006 SQL SERVER – Cursor to Kill All Process in Database I indeed wrote this cursor and when I often look back, I wonder how naive I was to write this. The reason for writing this cursor was to free up my database from any existing connection so I can do database operation. This worked fine but there can be a potentially big issue if there was any important transaction was killed by this process. There is another way to to achieve the same thing where we can use ALTER syntax to take database in single user mode. Read more about that over here and here. 2007 Rules of Third Normal Form and Normalization Advantage – 3NF The rules of 3NF are mentioned here Make a separate table for each set of related attributes, and give each table a primary key. If an attribute depends on only part of a multi-valued key, remove it to a separate table If attributes do not contribute to a description of the key, remove them to a separate table. Correct Syntax for Stored Procedure SP Sometime a simple question is the most important question. I often see in industry incorrectly written Stored Procedure. Few writes code after the most outer BEGIN…END and few writes code after the GO Statement. In this brief blog post, I have attempted to explain the same. 2008 Switch Between Result Pan and Query Pan – SQL Shortcut Many times when I am writing query I have to scroll the result displayed in the result set. Most of the developer uses the mouse to switch between and Query Pane and Result Pane. There are few developers who are crazy about Keyboard shortcuts. F6 is the keyword which can be used to switch between query pane and tabs of the result pane. Interesting Observation – Use of Index and Execution Plan Query Optimization is a complex game and it has its own rules. From the example in the article we have discovered that Query Optimizer does not use clustered index to retrieve data, sometime non clustered index provides optimal performance for retrieving Primary Key. When all the rows and columns are selected Primary Key should be used to select data as it provides optimal performance. 2009 Interesting Observation – TOP 100 PERCENT and ORDER BY If you pull up any application or system where there are more than 100 SQL Server Views are created – I am very confident that at one or two places you will notice the scenario wherein View the ORDER BY clause is used with TOP 100 PERCENT. SQL Server 2008 VIEW with ORDER BY clause does not throw an error; moreover, it does not acknowledge the presence of it as well. In this article we have taken three perfect examples and demonstrated which clause we should use when. Comma Separated Values (CSV) from Table Column A Very common question – How to create comma separated values from a table in the database? The answer is also very common if we use XML. Check out this article for quick learning on the same subject. Azure Start Guide – Step by Step Installation Guide Though Azure portal has changed a quite bit since I wrote this article, the concept used in this article are not old. They are still valid and many of the functions are still working as mentioned in the article. I believe this one article will put you on the track to use Azure! Size of Index Table for Each Index – Solution Earlier I have posted a small question on this blog and requested help from readers to participate here and provide a solution. The puzzle was to write a query that will return the size for each index that is on any particular table. We need a query that will return an additional column in the above listed query and it should contain the size of the index. This article presents two of the best solutions from the puzzle. 2010 Well, this week in 2010 was the week of puzzles as I posted three interesting puzzles. Till today I am noticing pretty good interesting in the puzzles. They are tricky but for sure brings a great value if you are a database developer for a long time. I suggest you go over this puzzles and their answers. Did you really know all of the answers? I am confident that reading following three blog post will for sure help you enhance the experience with T-SQL. SQL SERVER – Challenge – Puzzle – Usage of FAST Hint SQL SERVER – Puzzle – Challenge – Error While Converting Money to Decimal SQL SERVER – Challenge – Puzzle – Why does RIGHT JOIN Exists 2011 DVM sys.dm_os_sys_info Column Name Changed in SQL Server 2012 Have you ever faced a situation where something does not work? When you try to fix it - you enjoy fixing it and started to appreciate the breaking changes. Well, this was exactly I felt yesterday. Before I begin my story, I want to candidly state that I do not encourage anybody to use * in the SELECT statement. Now the disclaimer is over – I suggest you read the original story – you will love it! Get Directory Structure using Extended Stored Procedure xp_dirtree Here is the question to you – why would you do something in SQL Server where you can do the same task in command prompt much easily. Well, the answer is sometime there are real use cases when we have to do such thing. This is a similar example where I have demonstrated how in SQL Server 2012 we can use extended stored procedure to retrieve directory structure. 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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  • SQL SERVER – Weekly Series – Memory Lane – #006

    - by pinaldave
    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. 2006 This was my very first year of blogging so I was every day learning something new. As I have said many times, that blogging was never an intention. I had really not understood what exactly I am working on or beginning when I was beginning blogging in 2006. I had never knew that my life was going to change forever, once I started blogging. When I look back all of this year, I am happy that we are here together. 2007 IT Outsourcing to India – Top 10 Reasons Companies Outsource Outsourcing is about trust, collaboration and success. Helping other countries in need has been always the course of mankind, outsourcing is nothing different then that. With information technology and process improvements increasing the complexity, costs and skills required to accomplish routine tasks as well as challenging complex tasks, companies are outsourcing such tasks to providers who have the expertise to perform them at lower costs , with greater value and quality outcome. UDF – Remove Duplicate Chars From String This was a very interesting function I wrote in my early career. I am still using this function when I have to remove duplicate chars from strings. I have yet to come across a scenario where it does not work so I keep on using it till today. Please leave a comment if there is any better solution to this problem. FIX : Error : 3702 Cannot drop database because it is currently in use This is a very generic error when DROP Database is command is executed and the database is not dropped. The common mistake user is kept the connection open with this database and trying to drop the database. The database cannot be dropped if there is any other connection open along with it. It is always a good idea to take database in single user mode before dropping it. Here is the quick tutorial regarding how to bring the database in single user mode: Using T-SQL | Using SSMS. 2008 Install SQL Server 2008 – How to Upgrade to SQL Server 2008 – Installation Tutorial This was indeed one of the most popular articles in SQL Server 2008. Lots of people wanted to learn how to install SQL SErver 2008 but they were facing various issues while installation. I build this tutorial which becomes reference points for many. Default Collation of SQL Server 2008 What is the collation of SQL Server 2008 default installations? I often see this question confusing many experienced developers as well. Well the answer is in following image. Ahmedabad SQL Server User Group Meeting – November 2008 User group meetings are fun, now a days I am going to User Group meetings every week but there was a case when I have been just a beginner on this subject. The bug of the community was caught on me years ago when I started to present in Ahmedabad and Gandhinagar SQ LServer User Groups. 2009 Validate an XML document in TSQL using XSD My friend Jacob Sebastian wrote an excellent article on the subject XML and XSD. Because of the ‘eXtensible’ nature of XML (eXtensible Markup Language), often there is a requirement to restrict and validate the content of an XML document to a pre-defined structure and values. XSD (XML Schema Definition Language) is the W3C recommended language for describing and validating XML documents. SQL Server implements XSD as XML Schema Collections. Star Join Query Optimization At present, when queries are sent to very large databases, millions of rows are returned. Also the users have to go through extended query response times when joining multiple tables are involved with such queries. ‘Star Join Query Optimization’ is a new feature of SQL Server 2008 Enterprise Edition. This mechanism uses bitmap filtering for improving the performance of some types of queries by the effective retrieval of rows from fact tables. 2010 These puzzles are very interesting and intriguing – there was lots of interest on this subject. If you have free time this weekend. You may want to try them out. SQL SERVER – Challenge – Puzzle – Usage of FAST Hint (Solution)  SQL SERVER – Puzzle – Challenge – Error While Converting Money to Decimal (Solution)  SQL SERVER – Challenge – Puzzle – Why does RIGHT JOIN Exists (Open)  Additionally, I had great fun presenting SQL Server Performance Tuning seminar at fantastic locations in Hyderabad. Installing AdventeWorks Database This has been the most popular request I have received on my blog. Here is the quick video about how one can install AdventureWorks. 2011 Effect of SET NOCOUNT on @@ROWCOUNT There was an interesting incident once while I was presenting a session. I wrote a code and suddenly 10 hands went up in the air.  This was a bit surprise to me as I do not know why they all got alerted. I assumed that there should be something wrong with either project, screen or my display. However the real reason was very interesting – I suggest you read the complete blog post to understand this interesting scenario. Error: Deleting Offline Database and Creating the Same Name This is very interesting because once a user deletes the offline database the MDF and LDF file still exists and if the user attempts to create a new database with the same name it will give error. I found this very interesting and the blog explains the concept very quickly. Have you ever faced a similar situation? 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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  • Recursion VS memory allocation

    - by Vladimir Kishlaly
    Which approach is most popular in real-world examples: recursion or iteration? For example, simple tree preorder traversal with recursion: void preorderTraversal( Node root ){ if( root == null ) return; root.printValue(); preorderTraversal( root.getLeft() ); preorderTraversal( root.getRight() ); } and with iteration (using stack): Push the root node on the stack While the stack is not empty Pop a node Print its value If right child exists, push the node's right child If left child exists, push the node's left child In the first example we have recursive method calls, but in the second - new ancillary data structure. Complexity is similar in both cases - O(n). So, the main question is memory footprint requirement?

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  • SQL SERVER – Beginning New Weekly Series – Memory Lane – #002

    - by pinaldave
    Here is the list of curetted 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. 2006 Query to Find ByteSize of All the Tables in Database This was my second blog post and today I do not remember what was the business need which has made me build this query. It was built for SQL Server 2000 and it will not directly run on SQL Server 2005 or later version now. It measured the byte size of the tables in the database. This can be done in many different ways as well for example SP_HELPDB as well SP_HELP. I wish to build similar script in 2005 and later version. 2007 This week I had completed my – 1 Year (365 blogs) and very first 1 Million Views. I was pretty excited at that time with this new achievement. SQL SERVER Versions, CodeNames, Year of Release When I started with SQL Server I did not know all the names correctly for each version and I often used to get confused with this. However, as time passed by I started to remember all the codename as well. In this blog post I have not included SQL Server 2012′s code name as it was not released at the time. SQL Server 2012′s code name is Denali. Here is the question for you – anyone know what is the internal name of the SQL Server’s next version? Searching String in Stored Procedure I have already started to work with 2005 by this time and I was personally converting each of my stored procedures to SQL Server 2005 compatible. As we were upgrading from SQL Server 2000 to SQL Server 2005 we had to search each of the stored procedures and make sure that we remove incompatible code from it. For example, syscolumns of SQL Server 2000 was now being replaced by sys.columns of SQL Server 2005. This stored procedure was pretty helpful at that time. Later on I build few additional versions of the same stored procedure. Version 1: This version finds the Stored Procedures related to Table Version 2: This is specific version which works with SQL Server 2005 and later version 2008 Clear Drop Down List of Recent Connection From SQL Server Management Studio It happens to all of us when we connected to some remote client server and we never ever have to connect to it again. However, it keeps on bothering us that the name shows up in the list all the time. In this blog post I covered a quick tip about how we can remove the same. I also wrote a small article about How to Check Database Integrity for all Databases and there was a funny question from a reader requesting T-SQL code to refresh databases. 2009 Stored Procedure are Compiled on First Run – SP is taking Longer to Run First Time A myth is quite prevailing in the industry that Stored Procedures are pre-compiled and they should always run faster. It is not true. Stored procedures are compiled on very first execution of it and that is the reason why it takes longer when it executes first time. In this blog post I had a great time discussing the same concept. If you do not agree with it, you are welcome to read this blog post. Removing Key Lookup – Seek Predicate – Predicate – An Interesting Observation Related to Datatypes Performance Tuning is an interesting concept and my personal favorite one. In many blog posts I have described how to do performance tuning and how to improve the performance of the queries. In this quick quick tip I have explained how one can remove the Key Lookup and improve performance. Here are very relevant articles on this subject: Article 1 | Article 2 | Article 3 2010 Recycle Error Log – Create New Log file without a Server Restart During one of the consulting assignments I noticed DBA restarting server to create new log file. This is absolutely not necessary and restarting server might have many other negative impacts. There is a common sp_cycle_errorlog which can do the same task efficiently and properly. Have you ever used this SP or feature? Additionally I had a great time presenting on SQL Server Best Practices in SharePoint Conference. 2011 SSMS 2012 Reset Keyboard Shortcuts to Default It is very much possible that we mix up various SQL Server shortcuts and at times we feel like resetting it to default. In SQL Server 2012 it is not easy to do it, there is a process to follow and I enjoyed blogging about it. Fundamentals of Columnstore Index Columnstore index is introduced in SQL Server 2012 and have been a very popular subject. It increases the speed of the server dramatically as well can be an extremely useful feature with Datawharehousing. However updating the columnstore index is not as simple as a simple UPDATE statement. Read in a detailed blog post about how Update works with Columnstore Index. Additionally, you can watch a Quick Video on this subject. SQL Server 2012 New Features I had decided to explore SQL Server 2012 features last year and went through pretty much every single concept introduced in separate blog posts. Here are two blog posts where I describe how SQL Server 2012 functions works. Introduction to CUME_DIST – Analytic Functions Introduction to FIRST _VALUE and LAST_VALUE – Analytic Functions OVER clause with FIRST_VALUE and LAST_VALUE – Analytic Functions I indeed enjoyed writing about SQL Server 2012 functions last year. Have you gone through all the new features which are introduced in SQL Server 2012? If not, it is still not late to go through them. 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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  • Out of Memory when building an application

    - by Jacob Neal
    I have quite a major problem with my Multimedia Fusion 2 game. I finished it months ago, however, the only thing keeping me from finally compiling the game into an executable file is this error message that pops up every time I try to, simply saying, "Out of Memory". Its highly frustrating to be halted at this point by this message, and I tried everything I could come up with to fix it including compressing the runtime and sounds and increasing the proity of MMF2 all the way to realtime in the task manager. Im begging someone to toss me a bone on this problem, and any advice at all would be much appreciated.

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  • SQL SERVER – Weekly Series – Memory Lane – #004

    - by pinaldave
    Here is the list of curetted 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. 2006 Auto Generate Script to Delete Deprecated Fields in Current Database In early career everytime I have to drop a column, I had hard time doing it because I was scared what if that column was needed somewhere in the code. Due to this fear I never dropped any column. I just renamed the column. If the column which I renamed was needed afterwards it was very easy to rename it back again. However, it is not recommended to keep the deleted column renamed in the database. At every interval I used to drop the columns which was prefixed with specific word. This script is 6 years old but still works. Give it a look, I am open for improvements. 2007 Shrinking Truncate Log File – Log Full – Part 2 Shrinking database or mdf file is indeed bad thing and it creates lots of problems. However, once in a while there is legit requirement to shrink the log file – a very rare one. In the rare occasion shrinking or truncating the log file may be the only solution. However, one should make sure to take backup before and after the truncate or shrink as in case of a disaster they can be very useful. Remember that truncating log file will break the log chain and while restore it can create major issue. Anyway, use this feature with caution. 2008 Simple Use of Cursor to Print All Stored Procedures of Database Including Schema This is a very interesting requirement I used to face in my early career days, I needed to print all the Stored procedures of my database. Interesting enough I had written a cursor to do so. Today when I look back at this stored procedure, I believe there will be a much cleaner way to do the same task, however, I still use this SP quite often when I have to document all the stored procedures of my database. Interesting Observation about Order of Resultset without ORDER BY In industry many developers avoid using ORDER BY clause to display the result in particular order thinking that Index is enforcing the order. In this interesting example, I demonstrate that without using ORDER BY, same table and similar query can return different results. Query optimizer always returns results using any method which is optimized for performance. The learning is There is no order unless ORDER BY is used. 2009 Size of Index Table – A Puzzle to Find Index Size for Each Index on Table I asked this puzzle earlier where I asked how to find the Index size for each of the tables. The puzzle was very well received and lots of interesting answers were received. To answer this question I have written following blog posts. I suggest this weekend you try to solve this problem and see if you can come up with a better solution. If not, well here are the solutions. Solution 1 | Solution 2 | Solution 3 Understanding Table Hints with Examples Hints are options and strong suggestions specified for enforcement by the SQL Server query processor on DML statements. The hints override any execution plan the query optimizer might select for a query. The SQL Server Query optimizer is a very smart tool and it makes a better selection of execution plan. Suggesting hints to the Query Optimizer should be attempted when absolutely necessary and by experienced developers who know exactly what they are doing (or in development as a way to experiment and learn). Interesting Observation – TOP 100 PERCENT and ORDER BY I have seen developers and DBAs using TOP very causally when they have to use the ORDER BY clause. Theoretically, there is no need of ORDER BY in the view at all. All the ordering should be done outside the view and view should just have the SELECT statement in it. It was quite common that to save this extra typing by including ordering inside of the view. At several instances developers want a complete resultset and for the same they include TOP 100 PERCENT along with ORDER BY, assuming that this will simulate the SELECT statement with ORDER BY. 2010 SQLPASS Nov 8-11, 2010-Seattle – An Alternative Look at Experience In year 2010 I attended most prestigious SQL Server event SQLPASS between Nov 8-11, 2010 at Seattle. I have only one expression for the event - Best Summit Ever. Instead of writing about my usual routine or the event, I wrote about the interesting things I did and how I felt about it! When I go back and read it, I feel that this is the best event I attended in year 2010. Change Database Access to Single User Mode Using SSMS Image says all. 2011 SQL Server 2012 has introduced new analytic functions. These functions were long awaited and I am glad that they are now here. Before when any of this function was needed, people used to write long T-SQL code to simulate these functions. But now there’s no need of doing so. Having available native function also helps performance as well readability. Function SQLAuthority MSDN CUME_DIST CUME_DIST CUME_DIST FIRST_VALUE FIRST_VALUE FIRST_VALUE LAST_VALUE LAST_VALUE LAST_VALUE LEAD LEAD LEAD LAG LAG LAG PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_CONT PERCENTILE_DISC PERCENTILE_DISC PERCENTILE_DISC PERCENT_RANK PERCENT_RANK PERCENT_RANK 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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  • Serverside memory efficiency and threading for a turn based game

    - by SkeletorFromEterenia
    Im programming on a turn based war-game for some years now (along with the engine) and Im having quite a hard time at figuring out what the games server architecture should look like, since most game server architecture articles I found focus either on FPS oder MMOGs, which doesn't really fit since I want many matches with 1- 16 players on my server, with each match being played in turn based mode. My chief concern is memory usage, since the most basic approach of loading every game that is being played completely into RAM should be quite inefficient, so is there a suitable strategy for selecting only the needed bits and loading them? Another question I got is how to design the threading on the server, since I think using only a single thread could be a problem due to the fact that the game or part of it might have to be loaded from the database. I would be very happy if you could share your knowledge or point me to material on this topic.

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  • How In-Memory Database Objects Affect Database Design: Hybrid Code

    - by drsql
    In my first attempts at building my code, I strictly went with either native or on-disk code. I specifically wrote the on-disk code to only use features that worked in-memory. This lead to one majorly silly bit of code, used to create system assigned key values. How would I create a customer number that was unique. We can’t use the Max(value) + 1 approach because it will be very hideous with MVCC isolation levels, since 100 connections might see the same value, leading to lots of duplication. You...(read more)

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  • loadparm.c:4864, leaking memory?

    - by RandomOzzy
    I’m running Ubuntu 14.04 Server with a LAMP stack, Samba, and FTP, no GUI, just SSHing into the server and working on it. I’m having trouble searching down a solution to this issue, but as far as I can Google for it, it might have something to do with Samba. no talloc stackframe at ../source3/param/loadparm.c:4864, leaking memory?? The warning doesn't pop up at any kind of regular intervals or in response to the same or repeated actions. It pops up between things I’m doing - changing directories, editing files, copying stuff, and it often pops up when I first log in. Has anyone got experience fixing this issue?

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  • Where my memory is alloced, Stack or Heap, Can I find it at Run-time?

    - by AKN
    I know that memory alloced using new, gets its space in heap, and so we need to delete it before program ends, to avoid memory leak. Let's look at this program... Case 1: char *MyData = new char[20]; _tcscpy(MyData,"Value"); . . . delete[] MyData; MyData = NULL; Case 2: char *MyData = new char[20]; MyData = "Value"; . . . delete[] MyData; MyData = NULL; In case 2, instead of allocating value to the heap memory, it is pointing to a string literal. Now when we do a delete it would crash, AS EXPECTED, since it is not trying to delete a heap memory. Is there a way to know where the pointer is pointing to heap or stack? By this the programmer Will not try to delete any stack memory He can investigate why does this ponter, that was pointing to a heap memory initially, is made to refer local literals? What happened to the heap memory in the middle? Is it being made to point by another pointer and delete elsewhere and all that?

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  • Hardware reserved memory issue

    - by Robert Koritnik
    I've seen lots of folks having problem with hardware reserved memory issue in Windows 7/Server 2008 R2. I have it myself but not as huge as others have. Problem description When you install Windows 7 (or its bigger brother Windows Server 2008 R2) your memory may not be fully utilised. If you look at Task Manager > Performance Tab > Resource Monitor > Memory Tab And scroll to the bottom of the list you will see a graphical representation of your memory. Some of it may be hardware reserved. Previous Windows versions didn't have this problem. System was able to utilise all memory available. Question Is there any solution to lower/remove hardware reserved memory? Sidenote I tried installing 32 and 64 bit versions but to no avail. I also tried both Windows: 7 and Server 2008 R2. But always get the same amount reserved by HW. On previous Windows versions I had more memory available because I'm simultaneously running 2 VMs on host (so three machines all together). And my memory peaks much higher now as it did on older versions.

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  • Linux CentOS strange memory readings

    - by user2008937
    I am actually a young junior sys admin. I have a question - i am trying to understand how linux deals with memory... while playing around different monitoring programs I found some strange thing. When I run top on my laptop it shows me that FIREFOX process with pid 8778 takes 18,3% of memory (%MEM column). grep "MemTotal" /proc/meminfo Above command give me 1848336kb/1024 = 1805megs of memory (its ok - i have 2 gigs of ram). So if the firefox process takes 18,3% of MEM(according to tops %MEM column) then it takes 0.183 * 1805 which is approximately 325mb of memory. Quite a lot as for firefox... But well, in Linux there are lots of shared libraries that programs commonly uses (like famous libc). And those libraries are added to memory utilization of every process that uses it in the system, despite they are actually reading same file(single object in memory). So top may show too big mem utilization because of those shared libraries. Well, it is time to use PMAP which should show us the real mem utilization of process. But.. pmap -d $(pidof firefox) mapped: 983460K writeable/private: 757164K shared: 66416K so pmap shows that 983460/1024=993MB of memory is mapped to this process. It is in fact much bigger than mem utilization showed by top. Whats wrong here? How pmap can show more than top? even when top adds also the shared libraries (which in fact are single objects in memory) for each process that uses it? and pmap omits it? Regards Krzysztof

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  • Objects leaking immediately from allocation using either new or [[Object alloc] init];

    - by Sam
    While running Instruments to find leaks in my code, after I've loaded a file and populate an NSMutableArray with new objects, leaks pop up! I am correctly releasing the objects. Sample code below: //NSMutableArray declared as a retained property in the parent class if(!mutableArray) mutableArray = [[NSMutableArray alloc] initWithCapacity:objectCount]; else [mutableArray removeAllObjects]; //Iterates through the read in data and populate the NSMutableArray for(int i = 0; i < objectCount; i++){ //Initializes a new object with data MyObject *object = [MyObject new]; //Adds the object to the mutableArray [mutableArray addObject:object]; //Releases the object [object release]; } I get a number of leaks from Instruments terminating at the addition of the 'object' into the 'mutableArray', but also including the allocation of the 'object' and the 'mutableArray'. I don't get it. Not to mention, this is happening on the first call of the enclosing method so the allocation of the NSMutableArray is being hit in the logic block, not the 'removeAllObjects' selector. Lastly, does Core Foundation have a major bug in it that randomly creates CFStrings and mismanages their memory? My code does not even use those, nor do the leaks where they occur have anything to do with my code. Almost all of my applications so far deal with OpenGL (in case anyone knows of a threading issue that arises from trying to synch the backend of the program with the front end of displaying the contents of an NSOpenGLView class or whatever it is).

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  • SQL SERVER – Weekly Series – Memory Lane – #051

    - 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 Explanation and Understanding NOT NULL Constraint NOT NULL is integrity CONSTRAINT. It does not allow creating of the row where column contains NULL value. Most discussed questions about NULL is what is NULL? I will not go in depth analysis it. Simply put NULL is unknown or missing data. When NULL is present in database columns, it can affect the integrity of the database. I really do not prefer NULL in the database unless they are absolutely necessary. Three T-SQL Script to Create Primary Keys on Table I have always enjoyed writing about three topics Constraint and Keys, Backup and Restore and Datetime Functions. Primary Keys constraints prevent duplicate values for columns and provides a unique identifier to each column, as well it creates clustered index on the columns. 2008 Get Numeric Value From Alpha Numeric String – UDF for Get Numeric Numbers Only SQL is great with String operations. Many times, I use T-SQL to do my string operation. Let us see User Defined Function, which I wrote a few days ago, which will return only Numeric values from Alpha Numeric values. Introduction and Example of UNION and UNION ALL It is very much interesting when I get requests from blog reader to re-write my previous articles. I have received few requests to rewrite my article SQL SERVER – Union vs. Union All – Which is better for performance? with examples. I request you to read my previous article first to understand what is the concept and read this article to understand the same concept with an example. Downgrade Database for Previous Version The main questions is how they can downgrade the from SQL Server 2005 to SQL Server 2000? The answer is : Not Possible. Get Common Records From Two Tables Without Using Join Following is my scenario, Suppose Table 1 and Table 2 has same column e.g. Column1 Following is the query, 1. Select column1,column2 From Table1 2. Select column1 From Table2 I want to find common records from these tables, but I don’t want to use the Join clause because for that I need to specify the column name for Join condition. Will you help me to get common records without using Join condition? I am using SQL Server 2005. Retrieve – Select Only Date Part From DateTime – Best Practice – Part 2 A year ago I wrote a post about SQL SERVER – Retrieve – Select Only Date Part From DateTime – Best Practice where I have discussed two different methods of getting the date part from datetime. Introduction to CLR – Simple Example of CLR Stored Procedure CLR is an abbreviation of Common Language Runtime. In SQL Server 2005 and later version of it database objects can be created which are created in CLR. Stored Procedures, Functions, Triggers can be coded in CLR. CLR is faster than T-SQL in many cases. CLR is mainly used to accomplish tasks which are not possible by T-SQL or can use lots of resources. The CLR can be usually implemented where there is an intense string operation, thread management or iteration methods which can be complicated for T-SQL. Implementing CLR provides more security to the Extended Stored Procedure. 2009 Comic Slow Query – SQL Joke Before Presentation After Presentation Enable Automatic Statistic Update on Database In one of the recent projects, I found out that despite putting good indexes and optimizing the query, I could not achieve an optimized performance and I still received an unoptimized response from the SQL Server. On examination, I figured out that the culprit was statistics. The database that I was trying to optimize had auto update of the statistics was disabled. Recently Executed T-SQL Query Please refer to blog post  query to recently executed T-SQL query on database. Change Collation of Database Column – T-SQL Script – Consolidating Collations – Extention Script At some time in your DBA career, you may find yourself in a position when you sit back and realize that your database collations have somehow run amuck, or are faced with the ever annoying CANNOT RESOLVE COLLATION message when trying to join data of varying collation settings. 2010 Visiting Alma Mater – Delivering Session on Database Performance and Career – Nirma Institute of Technology Everyone always dreams of visiting their school and college, where they have studied once. It is a great feeling to see the college once again – where you have spent the wonderful golden years of your time. College time is filled with studies, education, emotions and several plans to build a future. I consider myself fortunate as I got the opportunity to study at some of the best places in the world. Change Column DataTypes There are times when I feel like writing that I am a day older in SQL Server. In fact, there are many who are looking for a solution that is simple enough. Have you ever searched online for something very simple. I often do and enjoy doing things which are straight forward and easy to change. 2011 Three DMVs – sys.dm_server_memory_dumps – sys.dm_server_services – sys.dm_server_registry In this blog post we will see three new DMVs which are introduced in Denali. The DMVs are very simple and there is not much to describe them. So here is the simple game. I will be asking a question back to you after seeing the result of the each of the DMV and you help me to complete this blog post. A Simple Quiz – T-SQL Brain Trick If you have some time, I strongly suggest you try this quiz out as it is for sure twists your brain. 2012 List All The Column With Specific Data Types in Database 5 years ago I wrote script SQL SERVER – 2005 – List All The Column With Specific Data Types, when I read it again, it is very much relevant and I liked it. This is one of the script which every developer would like to keep it handy. I have upgraded the script bit more. I have included few additional information which I believe I should have added from the beginning. It is difficult to visualize the final script when we are writing it first time. Find First Non-Numeric Character from String The function PATINDEX exists for quite a long time in SQL Server but I hardly see it being used. Well, at least I use it and I am comfortable using it. Here is a simple script which I use when I have to identify first non-numeric character. Finding Different ColumnName From Almost Identitical Tables Well here is the interesting example of how we can use sys.column catalogue views and get the details of the newly added column. I have previously written about EXCEPT over here which is very similar to MINUS of Oracle. Storing Data and Files in Cloud – Dropbox – Personal Technology Tip I thought long and hard about doing a Personal Technology Tips series for this blog.  I have so many tips I’d like to share.  I am on my computer almost all day, every day, so I have a treasure trove of interesting tidbits I like to share if given the chance.  The only thing holding me back – which tip to share first?  The first tip obviously has the weight of seeming like the most important.  But this would mean choosing amongst my favorite tricks and shortcuts.  This is a hard task. 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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  • SQL SERVER – Weekly Series – Memory Lane – #048

    - 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 Order of Result Set of SELECT Statement on Clustered Indexed Table When ORDER BY is Not Used Above theory is true in most of the cases. However SQL Server does not use that logic when returning the resultset. SQL Server always returns the resultset which it can return fastest.In most of the cases the resultset which can be returned fastest is the resultset which is returned using clustered index. Effect of TRANSACTION on Local Variable – After ROLLBACK and After COMMIT One of the Jr. Developer asked me this question (What will be the Effect of TRANSACTION on Local Variable – After ROLLBACK and After COMMIT?) while I was rushing to an important meeting. I was getting late so I asked him to talk with his Application Tech Lead. When I came back from meeting both of them were looking for me. They said they are confused. I quickly wrote down following example for them. 2008 SQL SERVER – Guidelines and Coding Standards Complete List Download Coding standards and guidelines are very important for any developer on the path of a successful career. A coding standard is a set of guidelines, rules and regulations on how to write code. Coding standards should be flexible enough or should take care of the situation where they should not prevent best practices for coding. They are basically the guidelines that one should follow for better understanding. Download Guidelines and Coding Standards complete List Download Get Answer in Float When Dividing of Two Integer Many times we have requirements of some calculations amongst different fields in Tables. One of the software developers here was trying to calculate some fields having integer values and divide it which gave incorrect results in integer where accurate results including decimals was expected. Puzzle – Computed Columns Datatype Explanation SQL Server automatically does a cast to the data type having the highest precedence. So the result of INT and INT will be INT, but INT and FLOAT will be FLOAT because FLOAT has a higher precedence. If you want a different data type, you need to do an EXPLICIT cast. Renaming SP is Not Good Idea – Renaming Stored Procedure Does Not Update sys.procedures I have written many articles about renaming a tables, columns and procedures SQL SERVER – How to Rename a Column Name or Table Name, here I found something interesting about renaming the stored procedures and felt like sharing it with you all. The interesting fact is that when we rename a stored procedure using SP_Rename command, the Stored Procedure is successfully renamed. But when we try to test the procedure using sp_helptext, the procedure will be having the old name instead of new names. 2009 Insert Values of Stored Procedure in Table – Use Table Valued Function It is clear from the result set that , where I have converted stored procedure logic into the table valued function, is much better in terms of logic as it saves a large number of operations. However, this option should be used carefully. The performance of the stored procedure is “usually” better than that of functions. Interesting Observation – Index on Index View Used in Similar Query Recently, I was working on an optimization project for one of the largest organizations. While working on one of the queries, we came across a very interesting observation. We found that there was a query on the base table and when the query was run, it used the index, which did not exist in the base table. On careful examination, we found that the query was using the index that was on another view. This was very interesting as I have personally never experienced a scenario like this. In simple words, “Query on the base table can use the index created on the indexed view of the same base table.” Interesting Observation – Execution Plan and Results of Aggregate Concatenation Queries Working with SQL Server has never seemed to be monotonous – no matter how long one has worked with it. Quite often, I come across some excellent comments that I feel like acknowledging them as blog posts. Recently, I wrote an article on SQL SERVER – Execution Plan and Results of Aggregate Concatenation Queries Depend Upon Expression Location, which is well received in the community. 2010 I encourage all of you to go through complete series and write your own on the subject. If you write an article and send it to me, I will publish it on this blog with due credit to you. If you write on your own blog, I will update this blog post pointing to your blog post. SQL SERVER – ORDER BY Does Not Work – Limitation of the View 1 SQL SERVER – Adding Column is Expensive by Joining Table Outside View – Limitation of the View 2 SQL SERVER – Index Created on View not Used Often – Limitation of the View 3 SQL SERVER – SELECT * and Adding Column Issue in View – Limitation of the View 4 SQL SERVER – COUNT(*) Not Allowed but COUNT_BIG(*) Allowed – Limitation of the View 5 SQL SERVER – UNION Not Allowed but OR Allowed in Index View – Limitation of the View 6 SQL SERVER – Cross Database Queries Not Allowed in Indexed View – Limitation of the View 7 SQL SERVER – Outer Join Not Allowed in Indexed Views – Limitation of the View 8 SQL SERVER – SELF JOIN Not Allowed in Indexed View – Limitation of the View 9 SQL SERVER – Keywords View Definition Must Not Contain for Indexed View – Limitation of the View 10 SQL SERVER – View Over the View Not Possible with Index View – Limitations of the View 11 2011 Startup Parameters Easy to Configure If you are a regular reader of this blog, you must be aware that I have written about SQL Server Denali recently. Here is the quickest way to reach into the screen where we can change the startup parameters. Go to SQL Server Configuration Manager >> SQL Server Services >> Right Click on the Server >> Properties >> Startup Parameters 2012 Validating Unique Columnname Across Whole Database I sometimes come across very strange requirements and often I do not receive a proper explanation of the same. Here is the one of those examples. For example “Our business requirement is when we add new column we want it unique across current database.” Read the solution to this strange request in this blog post. Excel Losing Decimal Values When Value Pasted from SSMS ResultSet It is very common when users are coping the resultset to Excel, the floating point or decimals are missed. The solution is very much simple and it requires a small adjustment in the Excel. By default Excel is very smart and when it detects the value which is getting pasted is numeric it changes the column format to accommodate that. Basic Calculation and PEMDAS Order of Operation Read this interesting blog post for fantastic conversation about the subject. Copy Column Headers from Resultset – SQL in Sixty Seconds #027 – Video http://www.youtube.com/watch?v=x_-3tLqTRv0 Delete From Multiple Table – Update Multiple Table in Single Statement There are two questions which I get every single day multiple times. In my gmail, I have created standard canned reply for them. Let us see the questions here. I want to delete from multiple table in a single statement how will I do it? I want to update multiple table in a single statement how will I do it? Read the answer in the blog post. 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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  • 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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  • How to understand the memory usage and load average in linux server

    - by Tim
    Hi, I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the running processes occupies a very small percentage of memory (%MEM no more than 0.2%, and most just 0.0%), but how the total memory is almost used as in the fourth line of output ("Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers")? The sum of used percentage of memory over all processes seems unlikely to achieve almost 100%, doesn't it? (2) how to understand the load average on the first line ("load average: 14.04, 14.02, 14.00")? Thanks and regards! Edit: Thanks! I also really like to hear some rough numbers based on used percentage of memory to determine if a server is heavily loaded, since I once became the one who cramed the server without understanding the current load. Is swap regarded as almost the same as memory? For example, when memory and swap are almost of same size, if the memory is almost running out but the swap is still largely free, may I just view it as if the used percentage of memory + swap is still not high and run other new processes? How would you consider together CPU or memory (or memory + swap) usage? Do you become worried if either of them reaches too high or both? Output of top: $ top top - 12:45:33 up 19 days, 23:11, 18 users, load average: 14.04, 14.02, 14.00 Tasks: 484 total, 12 running, 472 sleeping, 0 stopped, 0 zombie Cpu(s): 36.7%us, 19.7%sy, 0.0%ni, 43.6%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 130766620k total, 130161072k used, 605548k free, 919300k buffers Swap: 63111312k total, 500556k used, 62610756k free, 124437752k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 6529 sanchez 18 -2 1075m 219m 13m S 100 0.2 13760:23 MATLAB 13210 timothy 18 -2 48336 37m 1216 R 100 0.0 3:56.75 absurdity 13888 timothy 18 -2 48336 37m 1204 R 100 0.0 2:04.89 absurdity 14542 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.34 absurdity 14544 timothy 18 -2 2888 2076 400 R 100 0.0 1:06.14 gatherData 6183 sanchez 18 -2 1133m 195m 13m S 100 0.2 13676:04 MATLAB 6795 sanchez 18 -2 1079m 210m 13m S 100 0.2 13734:26 MATLAB 10178 timothy 18 -2 48336 37m 1204 R 100 0.0 11:33.93 absurdity 12438 timothy 18 -2 48336 37m 1216 R 100 0.0 5:38.17 absurdity 13661 timothy 18 -2 48336 37m 1216 R 100 0.0 2:44.13 absurdity 14098 timothy 18 -2 48336 37m 1204 R 100 0.0 1:58.31 absurdity 14335 timothy 18 -2 48336 37m 1196 R 100 0.0 1:08.93 absurdity 14765 timothy 18 -2 48336 37m 1196 R 99 0.0 0:32.57 absurdity 13445 timothy 18 -2 48336 37m 1216 R 99 0.0 3:01.37 absurdity 28990 root 20 0 0 0 0 S 2 0.0 65:50.21 pdflush 12141 tim 18 -2 19380 1660 1024 R 1 0.0 0:04.04 top 1240 root 15 -5 0 0 0 S 0 0.0 16:07.11 kjournald 9019 root 20 0 296m 4460 2616 S 0 0.0 82:19.51 kdm_greet 1 root 20 0 4028 728 592 S 0 0.0 0:03.11 init 2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd 3 root RT -5 0 0 0 S 0 0.0 0:01.01 migration/0 4 root 15 -5 0 0 0 S 0 0.0 0:08.13 ksoftirqd/0 5 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/0 6 root RT -5 0 0 0 S 0 0.0 17:27.31 migration/1 7 root 15 -5 0 0 0 S 0 0.0 0:01.21 ksoftirqd/1 8 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/1 9 root RT -5 0 0 0 S 0 0.0 10:02.56 migration/2 10 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/2 11 root RT -5 0 0 0 S 0 0.0 0:00.00 watchdog/2 12 root RT -5 0 0 0 S 0 0.0 4:29.53 migration/3 13 root 15 -5 0 0 0 S 0 0.0 0:00.34 ksoftirqd/3

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  • Figuring Out Memory Leaks without Clang

    - by RoLYroLLs
    I'm trying to see if I can find some leaks myself in Apple's TopSongs app. Can someone help me out in at least one and how to identify what is in the Leaks reports and how I can get an idea on finding them? ie: I got one like this: # Category Event Type Timestamp Address Size Responsible Library Responsible Caller 0 GeneralBlock-448 Malloc 00:02.185 0x3f41220 448 libxml2.2.dylib xmlNewParserCtxt From what I can tell, the method xmlNewParserCtxt is the problem, and it's not releasing an object, hence Malloc. The responsible library tells me it's the libxml2.2.dylib library with the problem, which I can't edit. Am I heading in the right direction? If so, half the leaks are in that library and well, i can't edit that.

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