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  • Form Validation Options

    The steps involved in transmitting form data from the client to the Web server User loads web form. User enters data in to web form fields User clicks submit On submit page validates fields using JavaScript. If validation errors are found then the validation script stops the browser from canceling posting the data to the web server and displays error messages as needed. If the form passes the data validation process then the browser will URL encode the values of every field and post it to the server.  The server reads the posted data from the query string and then again validates the data just to ensure data consistency and to prevent any non-validated data because JavaScript was turned off on the clients browser from being inserted in to a database or passed on to other process. If the data passes the second validation check then the server side code will continue with the requested processes. In my opinion, it is mandatory to validate data using client side and server side validation as a fail over process. The client side validation allows users to correct any error before they are sent to the web server for processing, and this allows for an immediate response back to the user regarding data that is not correct or in the proper format that is desired. In addition, this prevents unnecessary interaction between the user and the web server and will free up the server over time compared to doing only server side validation. Server validation is the last line of defense when it comes to validation because you can check to ensure the user’s data is correct before it is used in a business process or stored to a database. Honestly, I cannot foresee a scenario where I would only want to use one form of validation over another especially with the current cost of creating and maintaining data. In my opinion, the redundant validation is well worth the overhead.

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  • How can I resolve this one application coming up with an "You don't have permission to use the application" error?

    - by morgant
    I've got a Mac OS X 10.6 Snow Leopard Server Open Directory Master with a user who's getting Mobility & Application managed preferences from a group (the only group they're a member of). The workstation is also running Mac OS X 10.6 Snow Leopard, when the user logs in and tries to run our primary application which they're explicitly allowed to run (via the group's preferences), it says "You don't have permission to use the application 'Blah'". Now, the application is added to the group's list of always allowed applications, unsigned (so a minor difference in application version or file contents shouldn't disallow it). It even lives in a subdirectory of /Applications which is in the list of folders to allow applications. I've run into this when logging this user into new workstations and the following usually works: Log them out Remove the following files from their mobile home folder on the workstation: /Library/Managed\ Preferences/, ~/.FileSync, ~/Library/Preferences/com.apple.finder.plist, and ~/Library/Preferences/com.apple.MCX.plist. Remove the following files from their network home folder on the server: ~/.FileSync, ~/Library/Preferences/com.apple.finder.plist, and ~/Library/Preferences/com.apple.MCX.plist. Log them back in on the workstation. However, this no longer resolves the issue. Their Home Sync preferences are set (on the group) to sync ~, but not the following files (manually, at login, and at logout... no background sync here): ~/.SymAVQSFile ~/NAVMac800QSFile ~/Library ~/.FileSync ~/.account Their Preferences Sync preferences are set (also on the group) to sync ~/Library & ~/Documents/Microsoft User Data, but not the following files (also manually, at login, and at logout... no background sync): ~/.SymAVQSFile ~/.Trash ~/.Trashes ~/Documents/Microsoft User Data/Entourage Temp ~/Library/Application Support/SyncServices ~/Library/Application Support/MobileSync ~/Library/Caches ~/Library/Calendars/Calendar Cache ~/Library/Logs ~/Library/Mail/AvailableFeeds ~/Library/Mail/Envelope Index ~/Library/Preferences/Macromedia/ ~/Library/Printers ~/Library/PubSub/Database ~/Library/PubSub/Downloads ~/Library/PubSub/Feeds ~/Library/Safari/Icons.db ~/Library/Safari/HistoryIndex.sk ~/Library/iTunes/iPhone Software Updates IMAP-* Exchange-* EWS-* Mac-* ~/Library/Preferences/ByHost ~/Library/Preferences/com.apple.dock.plist ~/Library/Preferences/com.apple.sitebarlists.plist ~/Library/Application Support/4D ~/Library/Preferences/com.apple.MCX.plist ~/.FileSync ~/.account Even with ~/Library/Preferences/com.apple.MCX.plist prevented from syncing during a Preferences Sync, it still seems to show up in the network home on the server frequently. Are there any other files other than ~/Library/Preferences/com.apple.MCX.plist that contain application Managed Preferences that might be causing this one app to be showing up as not allowed? Any ideas on how ~/Library/Preferences/com.apple.MCX.plist keeps getting sync'd back up the network home folder on the server? Update: I thought I had found a workaround this morning, but it also seemed to be extremely temporary. Basically, loking at /Library/Managed\ Preferences/[shortname]/com.apple.applicationaccess.new.plist I discovered that it didn't have an entry for the application in question, but /Library/Managed\ Preferences/[shortname]/complete.plist did. Naturally, I deleted com.apple.applicationaccess.new.plist, logged in again, and it worked... on one workstation. It failed on others, and after logging out & back in a couple more times it started failing on all of them again, even after further deletions of com.apple.applicationaccess.new.plist. Oddly, com.apple.applicationaccess.new.plist & complete.plist do both contain an entry for the application in question now, but it still says it's not allowed. Further Update: Okay, so I now have a reproducible workaround which seems to be required after every reboot of the workstation: Log in as the user (you'll discover you cannot launch the application in question). Fast User Switch to the local admin account on the workstation (we always have one on every machine). From that local admin account, run sudo mcxrefresh -n 'shortname' (logging out and back in as the user in question will not work). Fast User Switch back to the user (you'll still not be allowed to run the application). Log the user out and back in (you'll now be able to run the application in question.) Fast User Switch back to the local admin account, log it out, and log back in as the user in question. If you do all that exactly as described it'll keep working through log out & log back in, but NOT through a reboot. If, after a reboot, you try something like logging in as the local admin account, running sudo mcxrefresh -n 'shortname', logging out, then logging in as the user in question, it will NOT work. Yet Another Update We don't have any computer groups in our Open Directory, so it shouldn't be getting any conflicting settings from there. I ran sudo mcxquery -format xml -user shortname -group groupname before & after performing the aforementioned process to allow the application in question to be run and the results were identical (saved the result to files & diff'd... I'm not just guessing here). One Step Forward, Half a Step Back: When the Mac OS X 10.6.5 Server update was released, we upgraded our Open Directory Master to it as the changes included the following managed preferences fixes which I hoped might address this issue: Addresses an issue that could prevent managed preferences from being applied when a user logs in on a workstation that has been idle. Fixes an issue that could prevent administrators from bypassing client management settings on a workstation. This seemed to improve the situation slightly. The application in question now usually launches without error. If, and when it does launch with the "You don't have permission to use the application" error, logging the user out and back in seems to correct it. That said, we've since had to add a couple of applications to the user's ~/Applications/ directory and those are still prevented from launching. The workstations are running Mac OS X 10.6.4, the OD Master (which the workstations are bound to) is running Mac OS 10.6.5 Server (although there are two OD Replicas still running 10.6.4 Server), and we're using Workgroup Manager 10.6.3 (which is included with the Server Admin Tools 10.6.5 upgrade) to add the applications (unsigned, as always). This time, I've caught the following in /var/log/system.log when attempting to launch one of the allowed applications from ~/Applications: Dec 22 17:36:24 hostname parentalcontrolsd[43221]: -[ActivityTracker checkApp:csFlags:] [954:username] -- *** Incoming app appears to be masquerading as white listed app and failed signature validation: /Users/username/Applications/FileMaker Pro 5.5/FileMaker Pro.app/Contents/MacOS/FileMaker Pro. Note: This may be a valid app of a different version than what was whitelisted (on a different volume?) Dec 22 17:36:24 hostname [0x0-0xa42a42].com.filemaker.filemakerpro[43304]: launch of /Users/username/Applications/FileMaker Pro 5.5/FileMaker Pro.app/Contents/MacOS/FileMaker Pro was blocked Dec 22 17:36:24 hostname com.apple.launchd.peruser.1340[6375] ([0x0-0xa42a42].com.filemaker.filemakerpro[43304]): Exited with exit code: 255 Dec 22 17:36:24 hostname parentalcontrolsd[43221]: -[ActivityTracker(Private) _removeAppFromWhiteList:] [1362:username] -- *** Couldn't find local user record Running sudo mcxquery -format xml -user username -group groupname includes the following entry for FileMaker Pro 5.5 (and appears to include a full integration of the user's application whitelist & group's application whitelist): <dict> <key>bundleID</key> <string>com.filemaker.filemakerpro</string> <key>displayName</key> <string>FileMaker Pro</string> </dict> Note the lack of <key>appID</key><data> ... </data> which seems to specify a signed application. While whitelisted directories also appear to be correctly listed in the results, they too do not actually allow the applications to be run either. What is going on here?! Where else should I be looking?

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  • User/Group Policies in Windows 2000 domain controller

    - by Chris
    In Server 2000 active directory, I have 5 groups of users and every user has different policies. The problem is that a different desktop loads for only one specific user no matter what changes I make in administrative templates. If I copy this user profile and paste it into another group with a different name, windows workaround loads as it should, but some policies are not applied. Does anybody know a way to solve this problem instead of creating a new group and user from scratch?

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  • How far should one take e-mail address validation?

    - by Mike Tomasello
    I'm wondering how far people should take the validation of e-mail address. My field is primarily web-development, but this applies anywhere. I've seen a few approaches: simply checking if there is an "@" present, which is dead simply but of course not that reliable. a more complex regex test for standard e-mail formats a full regex against RFC 2822 - the problem with this is that often an e-mail address might be valid but it is probably not what the user meant DNS validation SMTP validation As many people might know (but many don't), e-mail addresses can have a lot of strange variation that most people don't usually consider (see RFC 2822 3.4.1), but you have to think about the goals of your validation: are you simply trying to ensure that an e-mail address can be sent to an address, or that it is what the user probably meant to put in (which is unlikely in a lot of the more obscure cases of otherwise 'valid' addresses). An option I've considered is simply giving a warning with a more esoteric address but still allowing the request to go through, but this does add more complexity to a form and most users are likely to be confused. While DNS validation / SMTP validation seem like no-brainers, I foresee problems where the DNS server/SMTP server is temporarily down and a user is unable to register somewhere, or the user's SMTP server doesn't support the required features. How might some experienced developers out here handle this? Are there any other approaches than the ones I've listed? Edit: I completely forgot the most obvious of all, sending a confirmation e-mail! Thanks to answerers for pointing that one out. Yes, this one is pretty foolproof, but it does require extra hassle on the part of everyone involved. The user has to fetch some e-mail, and the developer needs to remember user data before they're even confirmed as valid.

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  • How to filter specific symbols(Only defined in dll/Exe/lib) using dia2dump

    - by Usman
    Hello, I need my all defined symbols (functions) in certain DLL/EXE/lib. I dont need Kernel or other OS layers symbols. I dont need all other stuf, only which's defined by my own DLL or EXE which I am giving it as PDB. But it shows EVERYTHING kernel related,OS related and balah blah endless list(sky is the limit).. I only required defined in my DLL, EXE or lib. How???? Regards Usman

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  • Why is my javascript function sometimes "not defined"?

    - by harpo
    Problem: I call my javascript function, and sometimes I get the error 'myFunction is not defined'. But it is defined. For example. I'll occasionally get 'copyArray is not defined' even in this example: function copyArray( pa ) { var la = []; for (var i=0; i < pa.length; i++) la.push( pa[i] ); return la; } Function.prototype.bind = function( po ) { var __method = this; var __args = []; // sometimes errors -- in practice I inline the function as a workaround __args = copyArray( arguments ); return function() { /* bind logic omitted for brevity */ } } As you can see, copyArray is defined right there, so this can't be about the order in which script files load. I've been getting this in situations that are harder to work around, where the calling function is located in another file that should be loaded after the called function. But this was the simplest case I could present, and appears to be the same problem. It doesn't happen 100% of the time, so I do suspect some kind of load-timing-related problem. But I have no idea what. @Hojou: That's part of the problem. The function in which I'm now getting this error is itself my addLoadEvent, which is basically a standard version of the common library function. @James: I understand that, and there is no syntax error in the function. When that is the case, the syntax error is reported as well. In this case, I am getting only the 'not defined' error. @David: The script in this case resides in an external file that is referenced using the normal <script src="file.js"></script> method in the page's head section. @Douglas: Interesting idea, but if this were the case, how could we ever call a user-defined function with confidence? In any event, I tried this and it didn't work. @sk: This technique has been tested across browsers and is basically copied from the prototype library.

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  • Detecting first time login of user into application (Google Appengine)

    - by Jake
    My app requires users to login using their google account. I have this set in my App.yamp file: url: /user/.* script: user.py login: required Now when any user tries to access files under /user/secret.py he will need to authenticate via google, which will redirect the user back to /user/secret.py after successful authentication. Now the problem I am facing is when the user is redirected back to the app, I cannot be sure if this is the first time the user has logged in or is it a regular user to my site who has come back again from just the user object which google passes using users.get_current_user() . I thus need to maintain state in the datastore to check if the user already exists or not everytime. If he does not exist i need to create a new entry with other application specific settings. My question is: Is there some easier way to handle this? without having to query the datastore to figure if this is a first time user or a regular one?

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  • Size already defined

    - by John Smith
    I was messing with my Objective-C++ namespace today. I found that Handle, Size and Duration are already defined in ObjC++. What are they defined to be and where are they defined? I have only #imported Foundation/Foundation.h

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  • Objects in JavaScript defined and undefined at the same time (in a FireFox extension)

    - by Alexey Romanov
    I am chasing down a bug in a FireFox extension. I've finally managed to see it for myself (I've only had reports before) and I can't understand how what I saw is possible. One error message from my extension in the Error Console is "gBrowser is not defined". This by itself would be surprising enough, since the overlay is over browser.xul and navigator.xul, and I expect gBrowser to be available from both. Even worse is the actual place where it happens: line 101 of nextplease.js. That is, inside the function isTopLevelDocument, which is only called from onContentLoaded, which is only called from onLoad here: gBrowser.addEventListener(this.loadType, function (event) { nextplease.loadListener.onContentLoaded(event); }, true); So gBrowser is defined in onLoad, but somehow undefined in isTopLevelDocument. When I tried to actually use the extension, I got another error: "nextplease is not defined". The interesting thing is that it happened on lines 853 and 857. That is, inside the functions nextplease.getNextLink = function () { nextplease.getLink(window.content, nextplease.NextPhrasesMap, nextplease.NextImagesMap, nextplease.isNextRegExp, nextplease.NEXT_SEARCH_TYPE); } nextplease.getPrevLink = function () { nextplease.getLink(window.content, nextplease.PrevPhrasesMap, nextplease.PrevImagesMap, nextplease.isPrevRegExp, nextplease.PREV_SEARCH_TYPE); } So nextplease is somehow defined enough to call these functions, but isn't defined inside them. Finally, executing typeof(nextplease) in Execute JS returns "object". Same for gBrowser. How can this happen? Any ideas?

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  • C error conflicting types

    - by ambika
    i have following error error : conflicting types for 'sprintf' error : conflicting types for 'vsprintf' error : conflicting types for 'vprintf' error : conflicting types for 'select' in my header file, the code is extern char *sprintf(char*,const char*,... )

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  • Auto convert java source to use generic rather than raw types

    - by Sam
    Is there a way/tool to auto convert Java source code from using raw types to using generic types? I have some legacy code with 677 references to raw types: ArrayList 47 Vector 420 Hashtable 61 Enumeration 64 Class 7 Iterator 78 TOTAL 677 Now I could manually look through the code to infer the generic types and replace, but that is going to take a long time.

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  • Replication - User defined table type not propogating to subscriber

    - by Aamod Thakur
    I created a User defined table type named tvp_Shipment with two columns (id and name) . generated a snapshot and the User defined table type was properly propogated to all the subscribers. I was using this tvp in a stored procedure and everything worked fine. Then I wanted to add one more column created_date to this table valued parameter.I dropped the stored procedure (from replication too) and also i dropped and recreated the User defined table type with 3 columns and then recreated the stored procedure and enabled it for publication When i generate a new snapshot, the changes in user defined table type are not propogated to the subscriber. The newly added column was not added to the subscription. the Error messages: The schema script 'usp_InsertAirSa95c0e23_218.sch' could not be propagated to the subscriber. (Source: MSSQL_REPL, Error number: MSSQL_REPL-2147201001) Get help: http://help/MSSQL_REPL-2147201001 Invalid column name 'created_date'. (Source: MSSQLServer, Error number: 207) Get help: http://help/207

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  • Stubbing a before_filter with RSpec

    - by TheDelChop
    Guys, I'm having trouble understanding why I can't seem to stub this controller method :load_user, since all of my tests fail if I change the actual implementation of :load_user to not return and instance of @user. Can anybody see why my stub (controller.stub!(:load_user).and_return(@user)) seems to fail to actually get called when RSpec makes a request to the controller? require 'spec_helper' describe TasksController do before(:each) do @user = Factory(:user) sign_in @user @task = Factory(:task) User.stub_chain(:where, :first).and_return(@user) controller.stub!(:load_user).and_return(@user) end #GET Index describe "GET Index" do before(:each) do @tasks = 7.times{Factory(:task, :user = @user)} @user.stub!(:tasks).and_return(@tasks) end it "should should find all of the tasks owned by a user" do @user.should_receive(:tasks).and_return(@tasks) get :index, :user_id = @user.id end it "should assign all of the user's tasks to the view" do get :index, :user_id = @user.id assigns[:tasks].should be(@tasks) end end #GET New describe "GET New" do before(:each) do @user.stub_chain(:tasks, :new).and_return(@task) end it "should return a new Task" do @user.tasks.should_receive(:new).and_return(@task) get :new, :user_id = @user.id end end #POST Create describe "POST Create" do before(:each) do @user.stub_chain(:tasks, :new).and_return(@task) end it "should create a new task" do @user.tasks.should_receive(:new).and_return(@task) post :create, :user_id = @user.id, :task = @task.to_s end it "saves the task" do @task.should_receive(:save) post :create, :user_id = @user.id, :task = @task end context "when the task is saved successfully" do before(:each) do @task.stub!(:save).and_return(true) end it "should set the flash[:notice] message to 'Task Added Successfully'"do post :create, :user_id = @user.id, :task = @task flash[:notice].should == "Task Added Successfully!" end it "should redirect to the user's task page" do post :create, :user_id = @user.id, :task = @task response.should redirect_to(user_tasks_path(@user.id)) end end context "when the task isn't saved successfully" do before(:each) do @task.stub(:save).and_return(false) end it "should return to the 'Create New Task' page do" do post :create, :user_id = @user.id, :task = @task response.should render_template('new') end end end it "should attempt to authenticate and load the user who owns the tasks" do context "when the tasks belong to the currently logged in user" do it "should set the user instance variable to the currently logged in user" do pending end end context "when the tasks belong to another user" do it "should set the flash[:notice] to 'Sorry but you can't view other people's tasks.'" do pending end it "should redirect to the home page" do pending end end end end class TasksController < ApplicationController before_filter :load_user def index @tasks = @user.tasks end def new @task = @user.tasks.new end def create @task = @user.tasks.new if @task.save flash[:notice] = "Task Added Successfully!" redirect_to user_tasks_path(@user.id) else render :action => 'new' end end private def load_user if current_user.id == params[:user_id].to_i @user = User.where(:id => params[:user_id]).first else flash[:notice] = "Sorry but you can't view other people's tasks." redirect_to root_path end end end Can anybody see why my stub doesnt' work? Like I said, my tests only pass if I make sure that load_user works, if not, all my tests fail which makes my think that RSpec isn't using the stub I created. Thanks, Joe

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  • Doxygen autolink not working to global enum types

    - by MeThinks
    I am trying to use Doxygen Automatic link generation to document some enum types. However, it is not generating links for the global enum types. It does generates links for the global struct types. Is there something I am missing? I am using the example provided on the link above. As required, I have documented the file in which the types are defined. update1: I am using Doxygen version 1.6.3 update2: global structs are ok

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  • Authlogic Help! Registering a new user when currently logged-in as a user not working.

    - by looloobs
    Hi Just as a disclaimer I am new to rails and programming in general so apologize for misunderstanding something obvious. I have Authlogic with activation up and running. So for my site I would like my users who are logged in to be able to register other users. The new user would pick their login and password through the activation email, but the existing user needs to put them in by email, position and a couple other attributes. I want that to be done by the existing user. The problem I am running into, if I am logged in and then try and create a new user it just tries to update the existing user and doesn't create a new one. I am not sure if there is some way to fix this by having another session start??? If that is even right/possible I wouldn't know how to go about implementing it. I realize without knowing fully about my application it may be difficult to answer this, but does this even sound like the right way to go about this? Am I missing something here? Users Controller: class UsersController < ApplicationController before_filter :require_no_user, :only => [:new, :create] before_filter :require_user, :only => [:show, :edit, :update] def new @user = User.new end def create @user = User.new if @user.signup!(params) @user.deliver_activation_instructions! flash[:notice] = "Your account has been created. Please check your e-mail for your account activation instructions!" redirect_to profile_url else render :action => :new end end def show @user = @current_user end def edit @user = @current_user end def update @user = @current_user # makes our views "cleaner" and more consistent if @user.update_attributes(params[:user]) flash[:notice] = "Account updated!" redirect_to profile_url else render :action => :edit end end end My User_Session Controller: class UserSessionsController < ApplicationController before_filter :require_no_user, :only => [:new, :create] before_filter :require_user, :only => :destroy def new @user_session = UserSession.new end def create @user_session = UserSession.new(params[:user_session]) if @user_session.save flash[:notice] = "Login successful!" if @user_session.user.position == 'Battalion Commander' : redirect_to battalion_path(@user_session.user.battalion_id) else end else render :action => :new end end def destroy current_user_session.destroy flash[:notice] = "Logout successful!" redirect_back_or_default new_user_session_url end end

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  • SQL SERVER – SOS_SCHEDULER_YIELD – Wait Type – Day 8 of 28

    - by pinaldave
    This is a very interesting wait type and quite often seen as one of the top wait types. Let us discuss this today. From Book On-Line: Occurs when a task voluntarily yields the scheduler for other tasks to execute. During this wait the task is waiting for its quantum to be renewed. SOS_SCHEDULER_YIELD Explanation: SQL Server has multiple threads, and the basic working methodology for SQL Server is that SQL Server does not let any “runnable” thread to starve. Now let us assume SQL Server OS is very busy running threads on all the scheduler. There are always new threads coming up which are ready to run (in other words, runnable). Thread management of the SQL Server is decided by SQL Server and not the operating system. SQL Server runs on non-preemptive mode most of the time, meaning the threads are co-operative and can let other threads to run from time to time by yielding itself. When any thread yields itself for another thread, it creates this wait. If there are more threads, it clearly indicates that the CPU is under pressure. You can fun the following DMV to see how many runnable task counts there are in your system. SELECT scheduler_id, current_tasks_count, runnable_tasks_count, work_queue_count, pending_disk_io_count FROM sys.dm_os_schedulers WHERE scheduler_id < 255 GO If you notice a two-digit number in runnable_tasks_count continuously for long time (not once in a while), you will know that there is CPU pressure. The two-digit number is usually considered as a bad thing; you can read the description of the above DMV over here. Additionally, there are several other counters (%Processor Time and other processor related counters), through which you can refer to so you can validate CPU pressure along with the method explained above. Reducing SOS_SCHEDULER_YIELD wait: This is the trickiest part of this procedure. As discussed, this particular wait type relates to CPU pressure. Increasing more CPU is the solution in simple terms; however, it is not easy to implement this solution. There are other things that you can consider when this wait type is very high. Here is the query where you can find the most expensive query related to CPU from the cache Note: The query that used lots of resources but is not cached will not be caught here. SELECT SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1, ((CASE qs.statement_end_offset WHEN -1 THEN DATALENGTH(qt.TEXT) ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)+1), qs.execution_count, qs.total_logical_reads, qs.last_logical_reads, qs.total_logical_writes, qs.last_logical_writes, qs.total_worker_time, qs.last_worker_time, qs.total_elapsed_time/1000000 total_elapsed_time_in_S, qs.last_elapsed_time/1000000 last_elapsed_time_in_S, qs.last_execution_time, qp.query_plan FROM sys.dm_exec_query_stats qs CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp ORDER BY qs.total_worker_time DESC -- CPU time You can find the most expensive queries that are utilizing lots of CPU (from the cache) and you can tune them accordingly. Moreover, you can find the longest running query and attempt to tune them if there is any processor offending code. Additionally, pay attention to total_worker_time because if that is also consistently higher, then  the CPU under too much pressure. You can also check perfmon counters of compilations as they tend to use good amount of CPU. Index rebuild is also a CPU intensive process but we should consider that main cause for this query because that is indeed needed on high transactions OLTP system utilized to reduce fragmentations. 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 of the discussions of Wait Stats in this blog is generic and varies 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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  • SQL SERVER – CXPACKET – Parallelism – Advanced Solution – Wait Type – Day 7 of 28

    - by pinaldave
    Earlier we discussed about the what is the common solution to solve the issue with CXPACKET wait time. Today I am going to talk about few of the other suggestions which can help to reduce the CXPACKET wait. If you are going to suggest that I should focus on MAXDOP and COST THRESHOLD – I totally agree. I have covered them in details in yesterday’s blog post. Today we are going to discuss few other way CXPACKET can be reduced. Potential Reasons: If data is heavily skewed, there are chances that query optimizer may estimate the correct amount of the data leading to assign fewer thread to query. This can easily lead to uneven workload on threads and may create CXPAKCET wait. While retrieving the data one of the thread face IO, Memory or CPU bottleneck and have to wait to get those resources to execute its tasks, may create CXPACKET wait as well. Data which is retrieved is on different speed IO Subsystem. (This is not common and hardly possible but there are chances). Higher fragmentations in some area of the table can lead less data per page. This may lead to CXPACKET wait. As I said the reasons here mentioned are not the major cause of the CXPACKET wait but any kind of scenario can create the probable wait time. Best Practices to Reduce CXPACKET wait: Refer earlier article regarding MAXDOP and Cost Threshold. De-fragmentation of Index can help as more data can be obtained per page. (Assuming close to 100 fill-factor) If data is on multiple files which are on multiple similar speed physical drive, the CXPACKET wait may reduce. Keep the statistics updated, as this will give better estimate to query optimizer when assigning threads and dividing the data among available threads. Updating statistics can significantly improve the strength of the query optimizer to render proper execution plan. This may overall affect the parallelism process in positive way. Bad Practice: In one of the recent consultancy project, when I was called in I noticed that one of the ‘experienced’ DBA noticed higher CXPACKET wait and to reduce them, he has increased the worker threads. The reality was increasing worker thread has lead to many other issues. With more number of the threads, more amount of memory was used leading memory pressure. As there were more threads CPU scheduler faced higher ‘Context Switching’ leading further degrading performance. When I explained all these to ‘experienced’ DBA he suggested that now we should reduce the number of threads. Not really! Lower number of the threads may create heavy stalling for parallel queries. I suggest NOT to touch the setting of number of the threads when dealing with CXPACKET wait. Read all the post in the Wait Types and Queue series. Note: The information presented here is from my experience and I no way claim it to be accurate. I suggest reading book on-line for further clarification. All the discussion of Wait Stats over here is generic and it varies by system to system. You are recommended to test this on development server before implementing to production server. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: DMV, 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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  • 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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  • SQL SERVER – IO_COMPLETION – Wait Type – Day 10 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 an IO-related wait types. From Book On-Line: Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits. IO_COMPLETION Explanation: Any tasks are waiting for I/O to finish. This is a good indication that IO needs to be looked over here. Reducing IO_COMPLETION wait: When it is an issue concerning the IO, one should look at the following things related to IO subsystem: Proper placing of the files is very important. We should check the file system for proper placement of files – LDF and MDF on a 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 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 the configuration of the HBA Queue Depth. In one of my recent projects, the SAN was performing really badly so the SAN administrator did not accept it. After some investigations, he agreed to change the HBA Queue Depth on development (test environment) set up and 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 possible that there are no proper indexes in the system and 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 two articles that I wrote; they are 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) 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 Types, SQL White Papers, T SQL, Technology

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  • SQL SERVER – Speed Up! – Parallel Processes and Unparalleled Performance – TechEd 2012 India

    - by pinaldave
    TechEd India 2012 is just around the corner and I will be presenting there on two different session. SQL Server Performance Tuning is a very challenging subject that requires expertise in Database Administration and Database Development. I always have enjoyed talking about SQL Server Performance tuning subject. Just like doctors I like to call my every attempt to improve the performance of SQL Server queries and database server as a practice too. I have been working with SQL Server for more than 8 years and I believe that many of the performance tuning concept I have mastered. However, performance tuning is not a simple subject. However there are occasions when I feel stumped, there are occasional when I am not sure what should be the next step. When I face situation where I cannot figure things out easily, it makes me most happy because I clearly see this as a learning opportunity. I have been presenting in TechEd India for last three years. This is my fourth time opportunity to present a technical session on SQL Server. Just like every other year, I decided to present something different, something which I have spend years of learning. This time, I am going to present about parallel processes. It is widely believed that more the CPU will improve performance of the server. It is true in many cases. However, there are cases when limiting the CPU usages have improved overall health of the server. I will be presenting on the subject of Parallel Processes and its effects. I have spent more than a year working on this subject only. After working on various queries on multi-CPU systems I have personally learned few things. In coming TechEd session, I am going to share my experience with parallel processes and performance tuning. Session Details Title: Speed Up! – Parallel Processes and Unparalleled Performance (Add to Calendar) Abstract: “More CPU More Performance” – A  very common understanding is that usage of multiple CPUs can improve the performance of the query. To get maximum performance out of any query – one has to master various aspects of the parallel processes. In this deep dive session, we will explore this complex subject with a very simple interactive demo. An attendee will walk away with proper understanding of CX_PACKET wait types, MAXDOP, parallelism threshold and various other concepts. Date and Time: March 23, 2012, 12:15 to 13:15 Location: Hotel Lalit Ashok - Kumara Krupa High Grounds, Bengaluru – 560001, Karnataka, India. Add to Calendar Please submit your questions in the comments area and I will be for sure discussing them during my session. If I pick your question to discuss during my session, here is your gift I commit right now – SQL Server Interview Questions and Answers Book. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology Tagged: TechEd, TechEdIn

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  • SQL SERVER – BACKUPIO, BACKUPBUFFER – Wait Type – Day 14 of 28

    - by pinaldave
    Backup is the most important task for any database admin. Your data is at risk if you are not performing database backup. Honestly, I have seen many DBAs who know how to take backups but do not know how to restore it. (Sigh!) In this blog post we are going to discuss about one of my real experiences with one of my clients – BACKUPIO. When I started to deal with it, I really had no idea how to fix the issue. However, after fixing it at two places, I think I know why this is happening but at the same time, I am not sure the fix is the best solution. The reality is that the fix is not a solution but a workaround (which is not optimal, but get your things done). From Book On-Line: BACKUPIO Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount. BACKUPBUFFER Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount. BACKUPIO and BACKUPBUFFER Explanation: This wait stats will occur when you are taking the backup on the tape or any other extremely slow backup system. Reducing BACKUPIO and BACKUPBUFFER wait: In my recent consultancy, backup on tape was very slow probably because the tape system was very old. During the time when I explained this wait type reason in the consultancy, the owners immediately decided to replace the tape drive with an alternate system. They had a small SAN enclosure not being used on side, which they decided to re-purpose. After a week, I had received an email from their DBA, saying that the wait stats have reduced drastically. At another location, my client was using a third party tool (please don’t ask me the name of the tool) to take backup. This tool was compressing the backup along with taking backup. I have had a very good experience with this tool almost all the time except this one sparse experience. When I tried to take backup using the native SQL Server compressed backup, there was a very small value on this wait type and the backup was much faster. However, when I attempted with the third party backup tool, this value was very high again and was taking much more time. The third party tool had many other features but the client was not using these features. We end up using the native SQL Server Compressed backup and it worked very well. If I get to see this higher in my future consultancy, I will try to understand this wait type much more in detail and so probably I would able to come to some solid solution. 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 discussion of Wait Stats in this blog is generic and varies 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 Server, SQL Tips and Tricks, SQL Wait Stats, SQL Wait Types, T SQL, Technology

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