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  • SQL SERVER – ASYNC_IO_COMPLETION – Wait Type – Day 11 of 28

    - by pinaldave
    For any good system three things are vital: CPU, Memory and IO (disk). Among these three, IO is the most crucial factor of SQL Server. Looking at real-world cases, I do not see IT people upgrading CPU and Memory frequently. However, the disk is often upgraded for either improving the space, speed or throughput. Today we will look at another IO-related wait type. From Book On-Line: Occurs when a task is waiting for I/Os to finish. ASYNC_IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. If by any means your application that’s connected to SQL Server is processing the data very slowly, this type of wait can occur. Several long-running database operations like BACKUP, CREATE DATABASE, ALTER DATABASE or other operations can also create this wait type. Reducing ASYNC_IO_COMPLETION wait: When it is an issue related to IO, one should check for the following things associated to IO subsystem: Look at the programming and see if there is any application code which processes the data slowly (like inefficient loop, etc.). Note that it should be re-written to avoid this  wait type. Proper placing of the files is very important. We should check the file system for proper placement of the files – LDF and MDF on separate drive, TempDB on another separate drive, hot spot tables on separate filegroup (and on separate disk), etc. Check the File Statistics and see if there is a higher IO Read and IO Write Stall SQL SERVER – Get File Statistics Using fn_virtualfilestats. Check event log and error log for any errors or warnings related to IO. If you are using SAN (Storage Area Network), check the throughput of the SAN system as well as configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly and so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on the development setup (test environment). As soon as we changed the HBA Queue Depth to quite a higher value, there was a sudden big improvement in the performance. It is very likely to happen that there are no proper indexes on the system and yet there are lots of table scans and heap scans. Creating proper index can reduce the IO bandwidth considerably. If SQL Server can use appropriate cover index instead of clustered index, it can effectively reduce lots of CPU, Memory and IO (considering cover index has lesser columns than cluster table and all other; it depends upon the situation). You can refer to the following two articles I wrote that talk about how to optimize indexes: Create Missing Indexes Drop Unused Indexes Checking Memory Related Perfmon Counters SQLServer: Memory Manager\Memory Grants Pending (Consistent higher value than 0-2) SQLServer: Memory Manager\Memory Grants Outstanding (Consistent higher value, Benchmark) SQLServer: Buffer Manager\Buffer Hit Cache Ratio (Higher is better, greater than 90% for usually smooth running system) SQLServer: Buffer Manager\Page Life Expectancy (Consistent lower value than 300 seconds) Memory: Available Mbytes (Information only) Memory: Page Faults/sec (Benchmark only) Memory: Pages/sec (Benchmark only) Checking Disk Related Perfmon Counters Average Disk sec/Read (Consistent higher value than 4-8 millisecond is not good) Average Disk sec/Write (Consistent higher value than 4-8 millisecond is not good) Average Disk Read/Write Queue Length (Consistent higher value than benchmark is not good) Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and there is no way that I claim it to be accurate. I suggest reading Book OnLine for further clarification. All the discussions of Wait Stats in this blog are generic and vary from system to system. It is recommended that you test this on a development server before implementing it to a production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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  • JAVA image transfer problem

    - by user579098
    Hi, I have a school assignment, to send a jpg image,split it into groups of 100 bytes, corrupt it, use a CRC check to locate the errors and re-transmit until it eventually is built back into its original form. It's practically ready, however when I check out the new images, they appear with errors.. I would really appreciate if someone could look at my code below and maybe locate this logical mistake as I can't understand what the problem is because everything looks ok :S For the file with all the data needed including photos and error patterns one could download it from this link:http://rapidshare.com/#!download|932tl2|443122762|Data.zip|739 Thanks in advance, Stefan p.s dont forget to change the paths in the code for the image and error files package networks; import java.io.*; // for file reader import java.util.zip.CRC32; // CRC32 IEEE (Ethernet) public class Main { /** * Reads a whole file into an array of bytes. * @param file The file in question. * @return Array of bytes containing file data. * @throws IOException Message contains why it failed. */ public static byte[] readFileArray(File file) throws IOException { InputStream is = new FileInputStream(file); byte[] data=new byte[(int)file.length()]; is.read(data); is.close(); return data; } /** * Writes (or overwrites if exists) a file with data from an array of bytes. * @param file The file in question. * @param data Array of bytes containing the new file data. * @throws IOException Message contains why it failed. */ public static void writeFileArray(File file, byte[] data) throws IOException { OutputStream os = new FileOutputStream(file,false); os.write(data); os.close(); } /** * Converts a long value to an array of bytes. * @param data The target variable. * @return Byte array conversion of data. * @see http://www.daniweb.com/code/snippet216874.html */ public static byte[] toByta(long data) { return new byte[] { (byte)((data >> 56) & 0xff), (byte)((data >> 48) & 0xff), (byte)((data >> 40) & 0xff), (byte)((data >> 32) & 0xff), (byte)((data >> 24) & 0xff), (byte)((data >> 16) & 0xff), (byte)((data >> 8) & 0xff), (byte)((data >> 0) & 0xff), }; } /** * Converts a an array of bytes to long value. * @param data The target variable. * @return Long value conversion of data. * @see http://www.daniweb.com/code/snippet216874.html */ public static long toLong(byte[] data) { if (data == null || data.length != 8) return 0x0; return (long)( // (Below) convert to longs before shift because digits // are lost with ints beyond the 32-bit limit (long)(0xff & data[0]) << 56 | (long)(0xff & data[1]) << 48 | (long)(0xff & data[2]) << 40 | (long)(0xff & data[3]) << 32 | (long)(0xff & data[4]) << 24 | (long)(0xff & data[5]) << 16 | (long)(0xff & data[6]) << 8 | (long)(0xff & data[7]) << 0 ); } public static byte[] nextNoise(){ byte[] result=new byte[100]; // copy a frame's worth of data (or remaining data if it is less than frame length) int read=Math.min(err_data.length-err_pstn, 100); System.arraycopy(err_data, err_pstn, result, 0, read); // if read data is less than frame length, reset position and add remaining data if(read<100){ err_pstn=100-read; System.arraycopy(err_data, 0, result, read, err_pstn); }else // otherwise, increase position err_pstn+=100; // return noise segment return result; } /** * Given some original data, it is purposefully corrupted according to a * second data array (which is read from a file). In pseudocode: * corrupt = original xor corruptor * @param data The original data. * @return The new (corrupted) data. */ public static byte[] corruptData(byte[] data){ // get the next noise sequence byte[] noise = nextNoise(); // finally, xor data with noise and return result for(int i=0; i<100; i++)data[i]^=noise[i]; return data; } /** * Given an array of data, a packet is created. In pseudocode: * frame = corrupt(data) + crc(data) * @param data The original frame data. * @return The resulting frame data. */ public static byte[] buildFrame(byte[] data){ // pack = [data]+crc32([data]) byte[] hash = new byte[8]; // calculate crc32 of data and copy it to byte array CRC32 crc = new CRC32(); crc.update(data); hash=toByta(crc.getValue()); // create a byte array holding the final packet byte[] pack = new byte[data.length+hash.length]; // create the corrupted data byte[] crpt = new byte[data.length]; crpt = corruptData(data); // copy corrupted data into pack System.arraycopy(crpt, 0, pack, 0, crpt.length); // copy hash into pack System.arraycopy(hash, 0, pack, data.length, hash.length); // return pack return pack; } /** * Verifies frame contents. * @param frame The frame data (data+crc32). * @return True if frame is valid, false otherwise. */ public static boolean verifyFrame(byte[] frame){ // allocate hash and data variables byte[] hash=new byte[8]; byte[] data=new byte[frame.length-hash.length]; // read frame into hash and data variables System.arraycopy(frame, frame.length-hash.length, hash, 0, hash.length); System.arraycopy(frame, 0, data, 0, frame.length-hash.length); // get crc32 of data CRC32 crc = new CRC32(); crc.update(data); // compare crc32 of data with crc32 of frame return crc.getValue()==toLong(hash); } /** * Transfers a file through a channel in frames and reconstructs it into a new file. * @param jpg_file File name of target file to transfer. * @param err_file The channel noise file used to simulate corruption. * @param out_file The name of the newly-created file. * @throws IOException */ public static void transferFile(String jpg_file, String err_file, String out_file) throws IOException { // read file data into global variables jpg_data = readFileArray(new File(jpg_file)); err_data = readFileArray(new File(err_file)); err_pstn = 0; // variable that will hold the final (transfered) data byte[] out_data = new byte[jpg_data.length]; // holds the current frame data byte[] frame_orig = new byte[100]; byte[] frame_sent = new byte[100]; // send file in chunks (frames) of 100 bytes for(int i=0; i<Math.ceil(jpg_data.length/100); i++){ // copy jpg data into frame and init first-time switch System.arraycopy(jpg_data, i*100, frame_orig, 0, 100); boolean not_first=false; System.out.print("Packet #"+i+": "); // repeat getting same frame until frame crc matches with frame content do { if(not_first)System.out.print("F"); frame_sent=buildFrame(frame_orig); not_first=true; }while(!verifyFrame(frame_sent)); // usually, you'd constrain this by time to prevent infinite loops (in // case the channel is so wacked up it doesn't get a single packet right) // copy frame to image file System.out.println("S"); System.arraycopy(frame_sent, 0, out_data, i*100, 100); } System.out.println("\nDone."); writeFileArray(new File(out_file),out_data); } // global variables for file data and pointer public static byte[] jpg_data; public static byte[] err_data; public static int err_pstn=0; public static void main(String[] args) throws IOException { // list of jpg files String[] jpg_file={ "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo1.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo2.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo3.jpg", "C:\\Users\\Stefan\\Desktop\\Data\\Images\\photo4.jpg" }; // list of error patterns String[] err_file={ "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 1.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 2.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 3.DAT", "C:\\Users\\Stefan\\Desktop\\Data\\Error Pattern\\Error Pattern 4.DAT" }; // loop through all jpg/channel combinations and run tests for(int x=0; x<jpg_file.length; x++){ for(int y=0; y<err_file.length; y++){ System.out.println("Transfering photo"+(x+1)+".jpg using Pattern "+(y+1)+"..."); transferFile(jpg_file[x],err_file[y],jpg_file[x].replace("photo","CH#"+y+"_photo")); } } } }

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  • Looking for a .NET data access layer

    - by Luke101
    Hello, I am looking for a data access layer for ado.net. I am not interested in linq, EF, NHibernate or any other ORM. Currently, I am using the data access layer from umbraco. The DAL is very good but they stopped developing it so i am looking for a different one. Does anyone know where I can find a list of DALs that I can test?

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  • Can I use a MIME type declaration to get an HTML file to open in MS Word?

    - by Toph
    Bill James wrote: I was able to render an HTML page with the MIME type set to "application/msword", which caused the browser to spawn Word which imported the html just fine, allowing edits and saving just as if I'd output a real Word doc. That sounds great to me, but I haven't been able to get it to work in any browser (Chrome/FF/Safari/Opera/IE on Win7 running Word 2010 beta). I tried changing the MIME type in the HTTP headers of several pages via Tamper Data to application/msword, and I tried using the http-equiv meta tag <meta http-equiv="Content-type" content="application/msword"> on a local HTML file I tried opening from the browser, but neither appeared to have any effect. I don't really have a clue with regard to HTTP headers and MIME types generally, so - any tips? Many thanks!

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  • iPhone: Save boolean into Core Data

    - by Nic Hubbard
    I have set up one of my core data attributes as a Boolean. Now, I need to set it, but XCode keeps telling me that it may not respond to setUseGPS. [ride setUseGPS: useGPS.on]; What is the method for setting a boolean in core data? All my other attributes are set this way, and they work great. So, not sure why a boolean does not work to be set this way?

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  • Stream data with Node.js

    - by Saif Bechan
    I want to know if it is possible to stream data from the server to the client with Node.js. From what I can understand all over the internet is that this has to be possible, yet I fail to find a correct example or solution. What I want is a single http post to node.js with AJAX. Than leave the connection open and continuously stream data to the client. The client will receive this stream and update the page continuously.

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  • Adding "System.Data.SQLite" as refernce.

    - by subash
    hi all, when i was building my project done in asp.net & c#.net ,it produced the error as "The type or namespace name 'SQLite' does not exist in the namespace 'System.Data' (are you missing an assembly reference?" so, when i tried to add it as reference ,i was not able to find "System.Data.SQLite" in my library . how to overcome this problem.?

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  • Selenium Data Driven Testing with C#

    - by Dinesh Kanojia
    HI All, i am Dinesh Kanojia and i am new in the Automate testing and i want to perform data driven testing in selenium using ASP.NET(C#),ajax and almost all the features of jquery so any one can give me the step how to perform data driven testing using c# or some demo through which i can perform my testing thanks in advance, warm regards, Dinesh.K

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  • Freely available dictionary data for Chinese, Japanese, CJK characters

    - by devio
    I am developing an online CJK character dictionary application, and already found the following databases: Unicode Unihan Database Jim Breen's JMDict and KanjiDic CEDict HanDeDict As I am looking for more data, web searches often lead me to online dictionaries, but not the data itself, using the same sources over again. If you know of any CJK-relevant downloadable dictionaries, please add them.

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  • SAS: rearrange field order in data step

    - by Dan
    In SAS 9, how can I in a simple data step, rearrange the order the field. Data set2; /*Something probably goes here*/ set set1; run; So if set1 has the following fields: Name Title Salary A Chief 40000 B Chief 45000 Then I can change the field order of set2 to: Title Salary Name Chief 40000 A Chief 45000 B Thanks, Dan

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  • Jquery Toggle & passing data

    - by Ross
    I have created a toggle button with jquery but I need to pass my $id so it can execute the mysql in toggle_visibility.php. how do I pass my variable from my tag ? Yes $("a.toggleVisibility").toggle( function () { $(this).html("No"); }, function () { $.ajax({ type: "POST", url: "toggle_visibility.php", data: "id", success: function(msg){ alert( "Data Saved: " + msg ); } }); $(this).html("Yes"); } );

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  • core data missing records iphone

    - by Sridhar
    Hello, I have a strange and serious problem. When I am working with core data (not saving or editing or anything) just accessing the data from entity. Sometime strangely a few records or all records are missing(deleting) from the entity when my application restarts. I checked them by opening the SQLite database. Can anyone have the same problem ? Thanks, Raghu

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  • Data Mining - Predictive Analysis

    - by IMHO
    We are looking at acquiring Data Mining software to primarily run predictive analysis processes. How does SQL Server Data Mining solution compares to other solutions like SPSS from IBM? Since SQL Server DM is included in SQL Server Enterprise license - what would be the justification to spend extra couple 100K to buy separate software just to do DM?

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  • C# Data Export Framework or tools.

    - by abmv
    Is there any data export framework in .net or something.I have need to device a tool kit to export legacy and data from older/legacy application to the new application under development,there are around three similar systems.To give you an idea the three have employee table.Is there any framework or dsl tool for this? Or I have to come up with all the code? How do you guys do it when you have customers whom you want to migrate to the new product ?

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  • Is it possible to have a wireless in-house NAS with wireless data transfer rates of equivalent to SATA speeds?

    - by techaddict
    Basically I would like to know, if it is possible to set up an NAS in my house to be accessed wirelessly, that can reach equivalent real-life data transfer speeds to USB 3.0 or an internal SATA hard drive. I have been wanting to do this for some time ( a couple of years now). Basically, this is what I want to do: Plug in a number of hard drives in an array, somewhere in my house, to be left plugged in and never have to be monitored. Ideally several terabytes. Whenever I am home, to have my computer and laptop configured to automatically find the NAS, as easy as plugging in an external hard drive - except completely wirelessly. Data transfer needs to be as seamless and quick as having added another internal hard drive in my laptop. Moreover, data should be able to accessed without having to copy it over - I should be able to wirelessly access the NAS and browse files, and open files directly from the NAS. For example, say I wanted to open a video - I should be able to play the video that is located on the NAS, directly from the NAS, completely wirelessly. If I wanted to open a .pdf file, I should be able to open it and read it directly from the NAS, as if it were located on my physical internal hard drive. Cost is important as well. Please tell me what equipment I need for this to be possible. I know you geniuses out there who can tell me if this is possible.

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  • C# Data Export Framwork or tools.

    - by abmv
    Is there any data export framework in .net or something.I have need to device a tool kit to export legacy and data from older/legacy application to the new application under development,there are around three similar systems.To give you an idea the three have employee table.Is there any framework or dsl tool for this? Or I have to come up with all the code? How do you guys do it when you have customers whom you want to migrate to the new product ?

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  • Spring.NET and ADO.NET Entity Data Model

    - by Jason
    Having defined an ADO.NET Entity Data Model, I can then instantiate it in a Repository class to query against the database. using (ApplicationEntities ctx = new ApplicationEntities()) { // query, CRUD, etc } However, that particular line of code becomes boilerplate in most of the methods in the repository class. Is it possible to just use Spring.NET to inject the Entity Data Model, either in the class or, even better, in an abstract parent class that all the repositories inherit from?

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  • Calculations in a table of data

    - by Christian W
    I have a table of data with survey results, and I want to do certain calculations on this data. The datastructure is somewhat like this: ____________________________________________________________________________________ | group |individual | key | key | key | | | |subkey|subkey|subkey|subkey|subkey|subkey|subkey|subkey|subkey| | | |q|q|q |q |q |q|q|q |q|q|q |q |q |q|q|q |q|q|q |q |q |q|q|q | |-------|-----------|-|-|--|--|---|-|-|--|-|-|--|--|---|-|-|--|-|-|--|--|---|-|-|--| | 1 | 0001 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 1 | 0002 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 1 | 0003 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 2 | 0004 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 2 | 0005 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 3 | 0006 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | | 4 | 0007 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 |1|7|5 |1 |3 |1|4|1 | ------------------------------------------------------------------------------------ Excuse my poor ascii skills... So, every individual belongs to a group, and has answered some questions. These questions are always grouped in keys and subkeys. Is there any simple method to calculate averages, deviations and similar based on the groupings. Something like public float getAverage(int key, int individual); float avg = getAverage(5,7); I think what I'm asking is what would be the best way to structure the data in C# to make it as easy as possible to work with? I have started making classes for every entity, but I got confused somewhere and something stopped working. So before I continue along this path, I was wondering if there are any other, better, ways of doing this? (Every individual can also have describing variables, like agegroup and such, but that's not important for the base functionality.) Our current solution does all calculations inline in the queries when requesting the data from the database. This works, but it's slow and the number of queries equals questions * individuals + keys * individuals, which could be alot if individual queries. Any suggestions?

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