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  • memory usage in iOS

    - by varun
    My app has a simple UI interface having simple buttons, date picker, picker view, table view, action sheet, toolbar, alert boxes etc. No images, no network access. Just plain simple UI. It accesses SQLite database a lot. ARC option is enabled. I have many questions to ask: In .h files, I am defining IBOutlets like @property(nonatomic, retain) IBOutlet UIButton *bt; Where do i need to do bt=nil? in didReceiveMemoryWarning or viewDidLoad Live Bytes in Instruments tool is 4-5MB. Is it enough or I need to reduce memory usage? If so, how can I do so? Please mention few important points. Also, what all need to be added to the following methods? applicationDidReceiveMemoryWarning UIApplicationDidReceiveMemoryWarningNotification

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  • How to reduce memory consumption an AWS EC2 t1.micro instance (free tier) ubuntu server 14.04 LTS EBS

    - by CMPSoares
    Hi I'm working on my bachelor thesis and for that I need to host a node.js web application on AWS, in order to avoid costs I'm using a t1.micro instance with 30GB disk space (from what I know it's the maximum I get in the free tier) which is barely used. But instead I have problems with memory consumption, it's using all of it. I tried the approach of creating a virtual swap area as mentioned at Why don't EC2 ubuntu images have swap? with these commands: sudo dd if=/dev/zero of=/var/swapfile bs=1M count=2048 && sudo chmod 600 /var/swapfile && sudo mkswap /var/swapfile && echo /var/swapfile none swap defaults 0 0 | sudo tee -a /etc/fstab && sudo swapon -a But this swap area isn't used somehow. Is something missing in this approach or is there another process of reducing the memory consumption in these type of AWS instances? Bottom-line: This originates server freezes and crashes and that's what I want to stop either by using the swap, reducing memory usage or both.

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  • What does this IIS memory dump mean? (reserved memory)

    - by Jesse
    My w3wp's are recycling every 60 seconds after using too much virtual memory. I ran the IIS Debug Diagnostic Tool to capture a memory dump before the worker process recycled; the most interesting part seems to be this: Virtual Allocation Summary Reserved memory 4.88 GBytes Committed memory 328.27 MBytes Mapped memory 17.36 MBytes Reserved block count 524 blocks Committed block count 1082 blocks Mapped block count 43 blocks So that 4.88 GBytes of reserved memory seems really big. But neither the DotNetMemoryAnalysis or the regular Memory Pressure Analyzer seems to tell me where that 4.88 GB went. How can I find out?

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  • Tomcat memory usage grows until crash with no GC run

    - by Phil
    I'm administrating a server running Tomcat that is getting a lot of traffic lately. If I monitor memory usage in Task Manager I can see the memory usage growing and eventually tomcat crashes around the 1GB mark. Here's the memory relevent bits I've set in Tomcat Properties (this is a Windows Server): Intial memory pool: 1024 MB Maximum memory pool: 1024 MB -XX:MaxPermSize=256M The weird thing is since these problems arose I've deployed Lambda Probe to the Tomcat instance and the memory usage values I see there are much lower, for example Task Manager might show 467MB used while the "Total" used in Probe is 212 MB. Also, the Maximum Total listed in Probe is 1.29GB, when I would have expected 1GB, the maximum memory set above. If I force the garbage collector to run using Probe, I can keep Tomcat from crashing for a while (indefinitely, AFAIK). So why doesn't the GC run automatically and stop Tomcat from crashing? Thanks.

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  • SQL 2008 Memory Usage

    - by Danilo Brambilla
    I have a SQL Server 2008 (ver 10.0.1600) running on a Windows Server 2008 R2 Enterprise server with 8 GB of physical ram. If I open Task Manager I can see on 'Physical Memory' section of 'Performance' tab that only 340 MB are Available of 8191 Total, but I can't see any process using such amount of memory. Please note SQL Server is memory limited to 6GB (Maximum Server Memory = 6000). If I open Sysinternals Process Explorer, I can see sqlsrvr.exe process has: Private Bytes: 227.000 K Working Set: 140.000 K Virtual Size: 8.762.000 K What does this means? Is there any way to free up this memory for other process? Why Virtual Size figure as allocated memory? I thought that Virtual Size was 'reserved memory' only.

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  • SQL 2008 Memory Usage

    - by Danilo Brambilla
    I have a SQL Server 2008 (ver 10.0.1600) running on a Windows Server 2008 R2 Enterprise server with 8 GB of physical ram. If I open Task Manager I can see on 'Physical Memory' section of 'Performance' tab that only 340 MB are Available of 8191 Total, but I can't see any process using such amount of memory. Please note SQL Server is memory limited to 6GB (Maximum Server Memory = 6000). If I open Sysinternals Process Explorer, I can see sqlsrvr.exe process has: Private Bytes: 227.000 K Working Set: 140.000 K Virtual Size: 8.762.000 K What does this means? Is there any way to free up this memory for other process? Why Virtual Size figure as allocated memory? I thought that Virtual Size was 'reserved memory' only.

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  • HP DL160 G6 memory PC3-10600R vs PC3-10600E

    - by Jeremy Hajek
    I am using a HP DL 160 G6 server that according to specs takes PC3 Registered or Unbuffered. When I combine the two types of memory below the system will not POST. When I use just the first type of memory listed the system will POST. I have two pieces of HP memory that came with the server labeled PC3-10600E-9-10-E0 and then I have some Crucial memory labeled PC3-10600R-9-10-B0 I wager that the R means Registered memory and the E means ECC - then shouldn't the crucial memory boot with the system according to the HP specs? Or does the E mean it is Unbuffered and therefore I shouldn't mix and match as according to this HP memory config doc?

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  • Motherboard not recognizing memory anymore

    - by root
    I bought some new RAM and installed it on my motherboard. But, the BIOS would not post. There's an LED on my motherboard that shows error codes, and it showed the error: No usable memory detected. So, I removed the new memory and reinstalled the old memory, thus restoring the computer back to its original configuration. But, the BIOS still would not post, still giving the error: No usable memory detected. I've ensured that the memory and power headers are seated properly. I've tried all possible combinations of memory slots, and I've also reset the CMOS, but the error remains the same. The computer was working fine before I tried upgrading the memory, and I originally assembled the computer myself. What are some possible causes of this problem?

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  • Why is my addSubview: method causing a leak?

    - by Nathan
    Okay, so I have done a ton of research on this and have been pulling my hair out for days trying to figure out why the following code leaks: [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; UIImage *comicImage = [self getCachedImage:[NSString stringWithFormat:@"%@%@%@",@"http://url/",comicNumber,@".png"]]; self.imageView = [[[UIImageView alloc] initWithImage:comicImage] autorelease]; [self.scrollView addSubview:self.imageView]; self.scrollView.contentSize = self.imageView.frame.size; self.imageWidth = [NSString stringWithFormat:@"%f",imageView.frame.size.width]; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; Both self.imageView and self.scrollView are @propety (nonatomic, retain) and released in my dealloc.. imageView isn't used anywhere else in the code. This code is also run in a thread off of the main thread. If I run this code on my device, it will quickly run out of memory if I continually load this view. However, I've found if I comment out the following line: [UIApplication sharedApplication].networkActivityIndicatorVisible = YES; UIImage *comicImage = [self getCachedImage:[NSString stringWithFormat:@"%@%@%@",@"http://url/",comicNumber,@".png"]]; self.imageView = [[[UIImageView alloc] initWithImage:comicImage] autorelease]; //[self.scrollView addSubview:self.imageView]; self.scrollView.contentSize = self.imageView.frame.size; self.imageWidth = [NSString stringWithFormat:@"%f",imageView.frame.size.width]; [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; Memory usage becomes stable, no matter how many times I load the view. I have gone over everything I can think to see why this is leaking, but as far as I can tell I have all my releases straight. Can anyone see what I am missing?

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  • Does SetFileBandwidthReservation affect memory-mapped file performance?

    - by Ghostrider
    Does this function affect Memory-mapped file performance? Here's the problem I need to solve: I have two applications competing for disk access: "reader" and "updater". Whole system runs on Windows Server 2008 R2 x64 "Updater" constantly accesses disk in a linear manner, updating data. They system is set up in such a way that updater always has infinite data to update. Consider that it is constantly approximating a solution of a huge set of equations that takes up entire 2TB disk drive. Updater uses ReadFile and WriteFile to process data in a linear fashion. "Reader" is occasionally invoked by user to get some pieces of data. Usually user would read several 4kb blocks from the drive and stop. Occasionally user needs to read up to 100mb sequentially. In exceptional cases up to several gigabytes. Reader maps files to memory to get data it needs. What I would like to achieve is for "reader" to have absolute priority so that "updater" would completely stop if needed so that "reader" could get the data user needs ASAP. Is this problem solvable by using SetPriorityClass and SetFileBandwidthReservation calls? I would really hate to put synchronization login in "reader" and "updater" and rather have the OS take care of priorities.

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  • ObjectiveC - Releasing objects added as parameters

    - by NobleK
    Ok, here goes. Being a Java developer I'm still struggling with the memory management in ObjectiveC. I have all the basics covered, but once in a while I encounter a challenge. What I want to do is something which in Java would look like this: MyObject myObject = new MyObject(new MyParameterObject()); The constructor of MyObject class takes a parameter of type MyParameterObject which I initiate on-the-fly. In ObjectiveC I tried to do this using following code: MyObject *myObject = [[MyObject alloc] init:[[MyParameterObject alloc] init]]; However, running the Build and Analyze tool this gives me a "Potential leak of an object" warning for the MyParameter object which indeed occurs when I test it using Instruments. I do understand why this happens since I am taking ownership of the object with the alloc method and not relinquishing it, I just don't know the correct way of doing it. I tried using MyObject *myObject = [[MyObject alloc] init:[[[MyParameterObject alloc] init] autorelease]]; but then the Analyze tool told me that "Object sent -autorelease too many times". I could solve the issue by modifying the init method of MyParameterObject to say return [self autorelease]; in stead of just return self;. Analyze still warnes about a potential leak, but it doesn't actually occur. However I believe that this approach violates the convention for managing memory in ObjectiveC and I really want to do it the right way. Thanx in advance.

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  • Fake ISAPI Handler to serve static files with extention that are rewritted by url rewriter

    - by developerit
    Introduction I often map html extention to the asp.net dll in order to use url rewritter with .html extentions. Recently, in the new version of www.nouvelair.ca, we renamed all urls to end with .html. This works great, but failed when we used FCK Editor. Static html files would not get serve because we mapped the html extension to the .NET Framework. We can we do to to use .html extension with our rewritter but still want to use IIS behavior with static html files. Analysis I thought that this could be resolve with a simple HTTP handler. We would map urls of static files in our rewriter to this handler that would read the static file and serve it, just as IIS would do. Implementation This is how I coded the class. Note that this may not be bullet proof. I only tested it once and I am sure that the logic behind IIS is more complicated that this. If you find errors or think of possible improvements, let me know. Imports System.Web Imports System.Web.Services ' Author: Nicolas Brassard ' For: Solutions Nitriques inc. http://www.nitriques.com ' Date Created: April 18, 2009 ' Last Modified: April 18, 2009 ' License: CPOL (http://www.codeproject.com/info/cpol10.aspx) ' Files: ISAPIDotNetHandler.ashx ' ISAPIDotNetHandler.ashx.vb ' Class: ISAPIDotNetHandler ' Description: Fake ISAPI handler to serve static files. ' Usefull when you want to serve static file that has a rewrited extention. ' Example: It often map html extention to the asp.net dll in order to use url rewritter with .html. ' If you want to still serve static html file, add a rewritter rule to redirect html files to this handler Public Class ISAPIDotNetHandler Implements System.Web.IHttpHandler Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest ' Since we are doing the job IIS normally does with html files, ' we set the content type to match html. ' You may want to customize this with your own logic, if you want to serve ' txt or xml or any other text file context.Response.ContentType = "text/html" ' We begin a try here. Any error that occurs will result in a 404 Page Not Found error. ' We replicate the behavior of IIS when it doesn't find the correspoding file. Try ' Declare a local variable containing the value of the query string Dim uri As String = context.Request("fileUri") ' If the value in the query string is null, ' throw an error to generate a 404 If String.IsNullOrEmpty(uri) Then Throw New ApplicationException("No fileUri") End If ' If the value in the query string doesn't end with .html, then block the acces ' This is a HUGE security hole since it could permit full read access to .aspx, .config, etc. If Not uri.ToLower.EndsWith(".html") Then ' throw an error to generate a 404 Throw New ApplicationException("Extention not allowed") End If ' Map the file on the server. ' If the file doesn't exists on the server, it will throw an exception and generate a 404. Dim fullPath As String = context.Server.MapPath(uri) ' Read the actual file Dim stream As IO.StreamReader = FileIO.FileSystem.OpenTextFileReader(fullPath) ' Write the file into the response context.Response.Output.Write(stream.ReadToEnd) ' Close and Dipose the stream stream.Close() stream.Dispose() stream = Nothing Catch ex As Exception ' Set the Status Code of the response context.Response.StatusCode = 404 'Page not found ' For testing and bebugging only ! This may cause a security leak ' context.Response.Output.Write(ex.Message) Finally ' In all cases, flush and end the response context.Response.Flush() context.Response.End() End Try End Sub ' Automaticly generated by Visual Studio ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable Get Return False End Get End Property End Class Conclusion As you see, with our static files map to this handler using query string (ex.: /ISAPIDotNetHandler.ashx?fileUri=index.html) you will have the same behavior as if you ask for the uri /index.html. Finally, test this only in IIS with the html extension map to aspnet_isapi.dll. Url rewritting will work in Casini (Internal Web Server shipped with Visual Studio) but it’s not the same as with IIS since EVERY request is handle by .NET. Versions First release

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  • Controlling read and write access width to memory mapped registers in C

    - by srking
    I'm using and x86 based core to manipulate a 32-bit memory mapped register. My hardware behaves correctly only if the CPU generates 32-bit wide reads and writes to this register. The register is aligned on a 32-bit address and is not addressable at byte granularity. What can I do to guarantee that my C (or C99) compiler will only generate full 32-bit wide reads and writes in all cases? For example, if I do a read-modify-write operation like this: volatile uint32_t* p_reg = 0xCAFE0000; *p_reg |= 0x01; I don't want the compiler to get smart about the fact that only the bottom byte changes and generate 8-bit wide read/writes. Since the machine code is often more dense for 8-bit operations on x86, I'm afraid of unwanted optimizations. Disabling optimizations in general is not an option.

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  • Out of memory when creating a lot of objects C#

    - by Bas
    I'm processing 1 million records in my application, which I retrieve from a MySQL database. To do so I'm using Linq to get the records and use .Skip() and .Take() to process 250 records at a time. For each retrieved record I need to create 0 to 4 Items, which I then add to the database. So the average amount of total Items that has to be created is around 2 million. while (objects.Count != 0) { using (dataContext = new LinqToSqlContext(new DataContext())) { foreach (Object objectRecord in objects) { // Create a list of 0 - 4 Random Items and add each Item to the Object for (int i = 0; i < Random.Next(0, 4); i++) { Item item = new Item(); item.Id = Guid.NewGuid(); item.Object = objectRecord.Id; item.Created = DateTime.Now; item.Changed = DateTime.Now; dataContext.InsertOnSubmit(item); } } dataContext.SubmitChanges(); } amountToSkip += 250; objects = objectCollection.Skip(amountToSkip).Take(250).ToList(); } Now the problem arises when creating the Items. When running the application (and not even using dataContext) the memory increases consistently. It's like the items are never getting disposed. Does anyone notice what I'm doing wrong? Thanks in advance!

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  • Setting synthesized arrays causing memory leaks using nested arrays

    - by webtoad
    Hello: Why is the following code causing a memory leak in an iPhone App? All of the initted objects below leak, including the arrays, the strings and the numbers. So, I'm thinking it has something to do with the the synthesized array property not releasing the object when I set the property again on the second and subsequent time this piece of code is called. Here is the code: "controller" (below) is my custom view controller class, which I have a reference to, and I am setting with this code snippet: sqlite3_stmt *statement; NSMutableArray *foo_IDs = [[NSMutableArray alloc] init]; NSMutableArray *foo_Names = [[NSMutableArray alloc] init]; NSMutableArray *foo_IDsBySection = [[NSMutableArray alloc] init]; NSMutableArray *foo_NamesBySection = [[NSMutableArray alloc] init]; // Get data: NSString *sql = @"select distinct p.foo_ID, p.foo_Name from foo as p "; if (sqlite3_prepare_v2(...) == SQLITE_OK) { while (sqlite3_step(statement) == SQLITE_ROW) { int p_id; NSString *foo_Name; p_id = sqlite3_column_int(statement, 0); char *str2 = (char *)sqlite3_column_text(statement, 1); foo_Name = [NSString stringWithCString:str2]; [foo_IDs addObject:[NSNumber numberWithInt:p_id]]; [foo_Names addObject:foo_Name]; } sqlite3_finalize(statement); } // Pass the array itself into another array: // (normally there is more than one array in each array) [foo_IDsBySection addObject: foo_IDs]; [foo_NamesBySection addObject: foo_Names]; [foo_IDs release]; [foo_Names release]; // Set some synthesized properties (of type NSArray, nonatomic, // retain) in controller: controller.foo_IDsBySection = foo_IDsBySection; controller.foo_NamesBySection = foo_NamesBySection; [foo_IDsBySection release]; [foo_NamesBySection release]; Thanks for any help!

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  • Out-of-memory algorithms for addressing large arrays

    - by reve_etrange
    I am trying to deal with a very large dataset. I have k = ~4200 matrices (varying sizes) which must be compared combinatorially, skipping non-unique and self comparisons. Each of k(k-1)/2 comparisons produces a matrix, which must be indexed against its parents (i.e. can find out where it came from). The convenient way to do this is to (triangularly) fill a k-by-k cell array with the result of each comparison. These are ~100 X ~100 matrices, on average. Using single precision floats, it works out to 400 GB overall. I need to 1) generate the cell array or pieces of it without trying to place the whole thing in memory and 2) access its elements (and their elements) in like fashion. My attempts have been inefficient due to reliance on MATLAB's eval() as well as save and clear occurring in loops. for i=1:k [~,m] = size(data{i}); cur_var = ['H' int2str(i)]; %# if i == 1; save('FileName'); end; %# If using a single MAT file and need to create it. eval([cur_var ' = cell(1,k-i);']); for j=i+1:k [~,n] = size(data{j}); eval([cur_var '{i,j} = zeros(m,n,''single'');']); eval([cur_var '{i,j} = compare(data{i},data{j});']); end save(cur_var,cur_var); %# Add '-append' when using a single MAT file. clear(cur_var); end The other thing I have done is to perform the split when mod((i+j-1)/2,max(factor(k(k-1)/2))) == 0. This divides the result into the largest number of same-size pieces, which seems logical. The indexing is a little more complicated, but not too bad because a linear index could be used. Does anyone know/see a better way?

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  • Memory Leakage using datatables

    - by Vix
    Hi, I have situation in which i'm compelled to retrieve 30,000 records each to 2 datatables.I need to do some manipulations and insert into records into the SQL server in Manipulate(dt1,dt2) function.I have to do this in 15 times as you can see in the for loop.Now I want to know what would be the effective way in terms of memory usage.I've used the first approach.Please suggest me the best approach. (1) for (int i = 0; i < 15; i++) { DataTable dt1 = GetInfo(i); DataTable dt2 = GetData(i); Manipulate(dt1,dt2); } (OR) (2) DataTable dt1 = new DataTable(); DataTable dt2 = new DataTable(); for (int i = 0; i < 15; i++) { dt1=null; dt2=null; dt1 = GetInfo(); dt2 = GetData(); Manipulate(dt1, dt2); } Thanks, Vix.

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  • Quickly and Easily Create Folders in Windows By Dragging and Dropping Files

    - by Lori Kaufman
    If you use iOS or Android devices, you’re familiar with the drag-and-drop method of creating folders. If you like that method of grouping files, you can get the same functionality on your Windows PC using a free utility, called Smart Folders. Smart Folders helps you quickly organize your files, such as images, documents, and audio files, without having to create separate folders before you move the files. Simply drag one file on top of another file to create a new folder. To use Smart Folders to easily create folders, double-click on the .exe file you downloaded (see the link at the end of this article). Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder? Why Your Android Phone Isn’t Getting Operating System Updates and What You Can Do About It How To Delete, Move, or Rename Locked Files in Windows

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  • Concatenating several .mp3 files into one .mp3

    - by Bakhtiyor
    As it was suggested here I am using cat command to concatenate several .mp3 files into one .mp3 file. Imagine, I have following .mp3 files in the current folder: 001001.mp3 001002.mp3 001003.mp3 001004.mp3 001005.mp3 or, like this: 096001.mp3 096002.mp3 096003.mp3 096004.mp3 I need to concatenate these .mp3 files in there ascending sequence, i.e. 001001.mp3+001002.mp3+001003.mp3+etc. In order to join these .mp3 files into one I am executing following command in the current folder: cat *.mp3 > final.mp3 I tested the final .mp3 file and it is what I am expected, but I need to be sure that above command picks files in there ascending sequence. Can I be sure that above command always concatenates files in the ascending sequence? Thank you Sir!

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  • SQL Server 2008 R2 still requires a trace flag for Lock Pages in Memory

    - by AaronBertrand
    Almost two years ago, I blogged that Lock Pages in Memory was finally available to Standard Edition customers (Enterprise Edition customers had long been deemed smart enough to not abuse this feature). In addition to applying a cumulative update (2005 SP3 CU4 or 2008 SP1 CU2), in order to take advantage of LPIM, you also had to enable trace flag 845. Since the trace flag isn't documented for SQL Server 2008 R2, several of us in the community assumed that it was no longer required (since it was introduced...(read more)

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  • SQL Server 2008 R2 still requires a trace flag for Lock Pages in Memory

    - by AaronBertrand
    Almost two years ago, I blogged that Lock Pages in Memory was finally available to Standard Edition customers (Enterprise Edition customers had long been deemed smart enough to not abuse this feature). In addition to applying a cumulative update (2005 SP3 CU4 or 2008 SP1 CU2), in order to take advantage of LPIM, you also had to enable trace flag 845. Since the trace flag isn't documented for SQL Server 2008 R2, several of us in the community assumed that it was no longer required (since it was introduced...(read more)

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  • SQL SERVER – Weekly Series – Memory Lane – #032

    - 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 Complete Series of Database Coding Standards and Guidelines SQL SERVER Database Coding Standards and Guidelines – Introduction SQL SERVER – Database Coding Standards and Guidelines – Part 1 SQL SERVER – Database Coding Standards and Guidelines – Part 2 SQL SERVER Database Coding Standards and Guidelines Complete List Download Explanation and Example – SELF JOIN When all of the data you require is contained within a single table, but data needed to extract is related to each other in the table itself. Examples of this type of data relate to Employee information, where the table may have both an Employee’s ID number for each record and also a field that displays the ID number of an Employee’s supervisor or manager. To retrieve the data tables are required to relate/join to itself. Insert Multiple Records Using One Insert Statement – Use of UNION ALL This is very interesting question I have received from new developer. How can I insert multiple values in table using only one insert? Now this is interesting question. When there are multiple records are to be inserted in the table following is the common way using T-SQL. Function to Display Current Week Date and Day – Weekly Calendar Straight blog post with script to find current week date and day based on the parameters passed in the function.  2008 In my beginning years, I have almost same confusion as many of the developer had in their earlier years. Here are two of the interesting question which I have attempted to answer in my early year. Even if you are experienced developer may be you will still like to read following two questions: Order Of Column In Index Order of Conditions in WHERE Clauses Example of DISTINCT in Aggregate Functions Have you ever used DISTINCT with the Aggregation Function? Here is a simple example about how users can do it. Create a Comma Delimited List Using SELECT Clause From Table Column Straight to script example where I explained how to do something easy and quickly. Compound Assignment Operators SQL SERVER 2008 has introduced new concept of Compound Assignment Operators. Compound Assignment Operators are available in many other programming languages for quite some time. Compound Assignment Operators is operator where variables are operated upon and assigned on the same line. PIVOT and UNPIVOT Table Examples Here is a very interesting question – the answer to the question can be YES or NO both. “If we PIVOT any table and UNPIVOT that table do we get our original table?” Read the blog post to get the explanation of the question above. 2009 What is Interim Table – Simple Definition of Interim Table The interim table is a table that is generated by joining two tables and not the final result table. In other words, when two tables are joined they create an interim table as resultset but the resultset is not final yet. It may be possible that more tables are about to join on the interim table, and more operations are still to be applied on that table (e.g. Order By, Having etc). Besides, it may be possible that there is no interim table; sometimes final table is what is generated when the query is run. 2010 Stored Procedure and Transactions If Stored Procedure is transactional then, it should roll back complete transactions when it encounters any errors. Well, that does not happen in this case, which proves that Stored Procedure does not only provide just the transactional feature to a batch of T-SQL. Generate Database Script for SQL Azure When talking about SQL Azure the most common complaint I hear is that the script generated from stand-along SQL Server database is not compatible with SQL Azure. This was true for some time for sure but not any more. If you have SQL Server 2008 R2 installed you can follow the guideline below to generate a script which is compatible with SQL Azure. Convert IN to EXISTS – Performance Talk It is NOT necessary that every time when IN is replaced by EXISTS it gives better performance. However, in our case listed above it does for sure give better performance. You can read about this subject in the associated blog post. Subquery or Join – Various Options – SQL Server Engine Knows the Best Every single time whenever there is a performance tuning exercise, I hear the conversation from developer where some prefer subquery and some prefer join. In this two part blog post, I explain the same in the detail with examples. Part 1 | Part 2 Merge Operations – Insert, Update, Delete in Single Execution MERGE is a new feature that provides an efficient way to do multiple DML operations. In earlier versions of SQL Server, we had to write separate statements to INSERT, UPDATE, or DELETE data based on certain conditions; however, at present, by using the MERGE statement, we can include the logic of such data changes in one statement that even checks when the data is matched and then just update it, and similarly, when the data is unmatched, it is inserted. 2011 Puzzle – Statistics are not updated but are Created Once Here is the quick scenario about my setup. Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated – WHY? Question to You – When to use Function and When to use Stored Procedure Personally, I believe that they are both different things - they cannot be compared. I can say, it will be like comparing apples and oranges. Each has its own unique use. However, they can be used interchangeably at many times and in real life (i.e., production environment). I have personally seen both of these being used interchangeably many times. This is the precise reason for asking this question. 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 Guess the Next Value – Puzzle 4 Simple Example to Configure Resource Governor – Introduction to Resource Governor Resource Governor is a feature which can manage SQL Server Workload and System Resource Consumption. We can limit the amount of CPU and memory consumption by limiting /governing /throttling on the SQL Server. If there are different workloads running on SQL Server and each of the workload needs different resources or when workloads are competing for resources with each other and affecting the performance of the whole server resource governor is a very important task. Tricks to Replace SELECT * with Column Names – SQL in Sixty Seconds #017 – Video  Retrieves unnecessary columns and increases network traffic When a new columns are added views needs to be refreshed manually Leads to usage of sub-optimal execution plan Uses clustered index in most of the cases instead of using optimal index It is difficult to debug SQL SERVER – Load Generator – Free Tool From CodePlex The best part of this SQL Server Load Generator is that users can run multiple simultaneous queries again SQL Server using different login account and different application name. The interface of the tool is extremely easy to use and very intuitive as well. A Puzzle – Swap Value of Column Without Case Statement Let us assume there is a single column in the table called Gender. The challenge is to write a single update statement which will flip or swap the value in the column. For example if the value in the gender column is ‘male’ swap it with ‘female’ and if the value is ‘female’ swap it with ‘male’. 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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  • Random memory corruption going undetected by memtest86

    - by sds
    Thinkpad t520; Ubuntu 12.04.1 LTS; 3.2.0-33-generic 16GB of ram Memtest86+ ran for 26 hours, 9 passes, no errors Booted into "recovery mode"; Ran fsck all filesystems - no errors; "check all packages" - no errors apparent random memory corruption: perl/R/chrome segfault every now and then, seemingly at random; sort(1) produces corrupt unsorted files. What could be possibly wrong and how do I debug it?

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  • MySQL Memory usage

    - by Rob Stevenson-Leggett
    Our MySQL server seems to be using a lot of memory. I've tried looking for slow queries and queries with no index and have halved the peak CPU usage and Apache memory usage but the MySQL memory stays constantly at 2.2GB (~51% of available memory on the server). Here's the graph from Plesk. Running top in the SSH window shows the same figures. Does anyone have any ideas on why the memory usage is constant like this and not peaks and troughs with usage of the app? Here's the output of the MySQL Tuning Primer script: -- MYSQL PERFORMANCE TUNING PRIMER -- - By: Matthew Montgomery - MySQL Version 5.0.77-log x86_64 Uptime = 1 days 14 hrs 4 min 21 sec Avg. qps = 22 Total Questions = 3059456 Threads Connected = 13 Warning: Server has not been running for at least 48hrs. It may not be safe to use these recommendations To find out more information on how each of these runtime variables effects performance visit: http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html Visit http://www.mysql.com/products/enterprise/advisors.html for info about MySQL's Enterprise Monitoring and Advisory Service SLOW QUERIES The slow query log is enabled. Current long_query_time = 1 sec. You have 6 out of 3059477 that take longer than 1 sec. to complete Your long_query_time seems to be fine BINARY UPDATE LOG The binary update log is NOT enabled. You will not be able to do point in time recovery See http://dev.mysql.com/doc/refman/5.0/en/point-in-time-recovery.html WORKER THREADS Current thread_cache_size = 0 Current threads_cached = 0 Current threads_per_sec = 2 Historic threads_per_sec = 0 Threads created per/sec are overrunning threads cached You should raise thread_cache_size MAX CONNECTIONS Current max_connections = 100 Current threads_connected = 14 Historic max_used_connections = 20 The number of used connections is 20% of the configured maximum. Your max_connections variable seems to be fine. INNODB STATUS Current InnoDB index space = 6 M Current InnoDB data space = 18 M Current InnoDB buffer pool free = 0 % Current innodb_buffer_pool_size = 8 M Depending on how much space your innodb indexes take up it may be safe to increase this value to up to 2 / 3 of total system memory MEMORY USAGE Max Memory Ever Allocated : 2.07 G Configured Max Per-thread Buffers : 274 M Configured Max Global Buffers : 2.01 G Configured Max Memory Limit : 2.28 G Physical Memory : 3.84 G Max memory limit seem to be within acceptable norms KEY BUFFER Current MyISAM index space = 4 M Current key_buffer_size = 7 M Key cache miss rate is 1 : 40 Key buffer free ratio = 81 % Your key_buffer_size seems to be fine QUERY CACHE Query cache is supported but not enabled Perhaps you should set the query_cache_size SORT OPERATIONS Current sort_buffer_size = 2 M Current read_rnd_buffer_size = 256 K Sort buffer seems to be fine JOINS Current join_buffer_size = 132.00 K You have had 16 queries where a join could not use an index properly You should enable "log-queries-not-using-indexes" Then look for non indexed joins in the slow query log. If you are unable to optimize your queries you may want to increase your join_buffer_size to accommodate larger joins in one pass. Note! This script will still suggest raising the join_buffer_size when ANY joins not using indexes are found. OPEN FILES LIMIT Current open_files_limit = 1024 files The open_files_limit should typically be set to at least 2x-3x that of table_cache if you have heavy MyISAM usage. Your open_files_limit value seems to be fine TABLE CACHE Current table_cache value = 64 tables You have a total of 426 tables You have 64 open tables. Current table_cache hit rate is 1% , while 100% of your table cache is in use You should probably increase your table_cache TEMP TABLES Current max_heap_table_size = 16 M Current tmp_table_size = 32 M Of 15134 temp tables, 9% were created on disk Effective in-memory tmp_table_size is limited to max_heap_table_size. Created disk tmp tables ratio seems fine TABLE SCANS Current read_buffer_size = 128 K Current table scan ratio = 2915 : 1 read_buffer_size seems to be fine TABLE LOCKING Current Lock Wait ratio = 1 : 142213 Your table locking seems to be fine The app is a facebook game with about 50-100 concurrent users. Thanks, Rob

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