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  • Debian on HP ProLiant server hangs (disk i/o is my guess)

    - by Martin
    I installed Debian (2.6.32-5-amd64) on my HP ProLiant MicroServer (purchased recently.) I also added 3 2tb hd in zfs. I've experienced several server froze. Sometimes it showed Soft lockup CUP stuck for 61s! Today I experienced a different problem (I think) and the message looked like this [431336.200002] Call Trace: [431336.200002] [<ffffffff812fcc7c>] ? _write_lock+0xe/0xf [431336.200002] [<ffffffff810d7a86>] ? __vmalloc_node+0x99/0xe2 : : and (in different screen) [431354.222318] Node 0 DMA32 free: 2064kB min:5520kB low:69900kB high:8280kB active_anon:181648kB inactive_anon:61728kB active_file:313152kB inactive_file:832456kB unevictable: 0kB isolated(anon): 0kB isolated(file):0kB present:1922596kB mlocked:0kB dirty:72kB writeback:0kB mapped:25620kB shmem:344kB slab_reclaimable:34460kB slab_unreclaimable:31400kB kernel_stack:2288kB pagetables:7556kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no [431354.222431] lowmem_reserve[]: 0 0 0 0 : : Is this a hardware problem? What tools/methods can I find out the source of the problem? I've used Debian for years but never had problem like this.

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  • Cannot access Domain Controller through VPN

    - by Markus
    In our small network there is a Windows 2008 R2 Domain Controller that also serves as Remote Access Server. For years, we could access this server and the resources in the network over a VPN connection without any problem. Since some time however, I am able to connect to the VPN, but my Windows 8 client (and another one I used for testing purposes) is not able to connect the domain controller afterwards. I can access any other server in the network, but there seems to be a problem regarding the trust between the client(s) and the server. If I connect the client to the network directly over a LAN cable, everything works as expected. Also I can connect to another server over VPN and open a RDP prompt to the DC without a problem. On the client, whenever I try to access the DC, I get an access denied message. I've tried to update the group policies both over VPN and LAN. Also, I've removed the client from the domain and re-added it. The client shows a message that Windows requires valid login information when connected to the VPN - but my credentials are valid. They work when I logon to the client when not connected to the VPN and also when connected to the LAN. Turning off the firewall on the client and the server did not change anything. DNS resolution works both on the server and the client. What else can I do to diagnose and solve the problem?

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  • php mail() function painfully slow on local development machine

    - by Michael B
    Background: If you have set up a local apache server for development purposes you may have run into the problem where sendmail takes a long time (at least one minute) to send emails. This is extremely frustrating if you are trying to debug a problem with an email you have generated. There are several forum posts on the internet that discuss this problem. However, none of theme described what to do in enough detail for my limited knowledge. Here are the steps that worked for me: 1) find your hostname (in case you've forgotten it) using this command: :~$ cat /hosts/hostname myhostname 2) edit the file /etc/hosts and make sure the first line is the following: 127.0.0.1 localhost.localdomain localhost myhostname 3) edit the sendmail configuration file ( /etc/mail/sendmail.cf in Ubuntu) and Uncomment the line #O HostsFile=/etc/hosts 4) Restart the computer. The computer should boot up much faster now and the mail() function should return almost immediately. HOWEVER, the emails won't actually be sent unless you follow step 5. 5) You must new use the sendmail '-f' option whenever using the mail function. For example: mail('[email protected]', 'the subject', 'the message', null, '[email protected]'); My question for my fellow serverfaulters is: What further changes can be made so that I don't have to use the sendmail -f option? Although it's not very hard to add the -f option, it is a problem when your CMS (such as Drupal) does not use the -f option when sending mail. You would need to hack a core module to add this option.

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  • windows server 2003 speed issues

    - by farzinSH
    I have a HP server with windows server 2003 and 50 windows XP clients. Since a week and a half the networks speed suddenly drop 2-3 times per day. It gets so slow that none of the clients could work with the HIS program installed on them. We tried so many different things such as replacing the hubs,switches and even some wires. Every time one of these changes solves the problem and the network goes back to its normal state. I checked everything. Even when I disconnected all the clients from the server and connected it to just one computer the problem still remained for 2 hours. I just narrowed down the problem to the couple of likely speculations as follows: viruses? (Updated Kaspersky running on the server shows none) server hardware failure? Physical memory usage on the server? (Because the last time the problem occurred none of the changes above solved the issue so I restarted the server an checked the physical memory usage which was 2 GBs. But I noticed it's increasing over time to over 9 GBs...the server has 16 GBs of RAM.) I surfed the internet and got nothing. Any help would do us a lot....thanks in advance

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  • computer randomly restarting. both in game and out of game

    - by eric
    first my specs are. AMD Phenom II x4 955 processor 3.2ghz 20gb ddr3 ram 4Gb Nvidia Geforce GTX 770 850w Corsair tx850w psu Gigabyte ud3 mobo Windows 7 professional I recently uprgraded my vid card to gtx770 and upgraded my psu to the 850w thats in it now. i did a reformat with the installation of the new gpu and psu and started fresh and only have a couple programs installed (diablo3, nvidia control panel, wow, and steam). all drivers are up to date and everything is hooked up correctly. the problem is it will randomly shut down. no blue screen. just turns itself straight off and reboots after a couple seconds. occasionally i will have to unplug the power cable from the psu for a few minutes then reconnect and it will start up. it seems pretty random. sometimes it does it when my pc is just sitting there on the home screen. and sometimes it does it during games. and sometimes it doesnt do it for days at a time. i noticed the psu felt hot so i put an extra fan blowing straight onto both the psu and gpu and neither feel overly hot after it shuts down now. could it just be that it is a psu problem. the psu was taken from another machine but wasnt having this problem in that machine. i have seen a few articles online about gtx770 doing the same thing. but i havent found any answers or solutions. any help will be appreciated. im sure the 850w is enough to power my machine, im just stumped and ran out of ideas to fix it. i have even returned the video card for another thinking it might have been an issue with that particular card, but still gettin the same problem.

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  • Strange network issue (ZIP file fails CRC test over VPN)

    - by Joe Schmoe
    We have a server in the office running Windows Server 2003 Our office is connected to our datacenter via hardware VPN (Linksys RV082 router in the office to CISCO router in the datacenter). There is a job that runs on the server in the office that does following: ZIP certain files from the server using 7Zip, copy ZIP file to a network share in the office and verify ZIP integrity, copy ZIP file to a network share in the data center and verify ZIP integrity. Problem is - verifying ZIP integrity for the file in the data center always fails. However, if I run 7Zip on the server in data center that exposes that share ZIP file verifies just fine, so it is not actually corrupted during copy operation. Additionally, I tried running ZIP on other computers in the office to verify ZIP file on datacenter file share and it verifies OK. I tried plugging server to the same network port where my workstation is connected using different cable (my workstation doesn't exhibit this problem) and ZIP verification still fails. So the problem is local to that specific server. On network adapter properties for the server in question there is no "Advanced" tab where one can usually configure a lot of network settings. Network card driver is up to date (Windows Update doesn't find anything newer and Lenovo website doesn't have any drivers for Windows 2003 for this computer model). Is there any other way to configure network setting via command line? What settings could be relevant to this problem?

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  • How do I disable DirectDraw and Direct3D acceleration on Windows 8? [closed]

    - by Favourite Chigozie Onwuemene
    Some old games that i would really like to play run slowly on some graphic drivers when direct3d acceleration is enabled. I have tried many suggestions but none seems to work. The only thing i have not tried is disabling direct3d acceleration. Is it possible to disable DirectDraw and Direct3D acceleration on my Windows 8 pc? There are certain bad versions of GeForce drivers that cause this problem. This is a problem in the drivers themselves and is unfortunately completely outside our control. The recommended way to fix this problem is to update your graphics card drivers (go to NVIDIA's web site for this). Alternatively, there is a workaround that alleviates or solves the slowdown problem altogether. Try this: Right-click on your desktop and select "Properties". Go to the "Settings" tab and click on "Advanced...". Click on the "Troubleshooting" tab and move the slider to the left until it says that all DirectDraw and Direct3D accelerations have been disabled (around the middle of the range). Finally, click on "OK". Note that this workaround might cause other games on your computer to slow down, so you may have to switch back and forth between settings, but it's certainly worth a try if you can't obtain an updated graphics driver. -source: interactionstudios

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  • What could possibly cause my computer to power down at random times?

    - by geoffreydv
    I have recently bought a new Power Supply and a new graphics card. My PC ran smoothly for a few months now but since a couple of days I'm having a strange problem. I am trying to isolate the problem to a specific piece of hardware (because if it's either the Power Supply or the Graphics card they are still under warranty). The problem started when I was playing a game (diablo 3). My PC suddenly powered down. I was unable to turn it on again by pressing the power button. I unplugged the power cable for a few seconds and plugged it back in. This time the pc powered on but the indication light turned orange instead of white as it normally does. The fans were not spinning and I did not see anything on my screen. After trying a couple of times I gave up. Two days later I tried again and this time the PC did boot up as usual. Everything looked okay until I tested if the problem was resolved by starting Diablo again. After about two minutes it powered down again as it did the first time. If I don't run any games my PC does power down after about 3-5 hours. Another fact that might be relevant: One time the PC did not shut down immediatly, instead first my graphics "powered down" but the music I was playing kept on playing. After about 20 seconds the pc powered down completely as usual. What I also noticed is that when I boot instantly after a power down, the chance of another power down occuring is much higher. Does anyone have an idea what could be causing this kind of behaviour or has a certain tool to diagnose the specific hardware parts? Thanks Specs: Memory: 6GB Processor: Intel i5 OS: Windows 7 64 bit The PC is a Dell Studio XPS 8100 with a replaced PSU and Graphics card: PSU: Corsair CX500 (500 watt) Graphics card: AMD Radeon 6850

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  • Adding a 2008 server to a 2003 Domain with DNS devolution?

    - by mvdwege
    I'm running into a problem adding a 2008 server to our existing 2003 domain, and as I am not a Windows admin, I'm not getting the problem here. Some reading around on Technet seems to indicate that DNS devolution is the issue. Here's the setup: DNS for the entire company is hosted on a Unix server running Bind, including the service records for the Windows domain. Our toplevel is company.local, and functional domains are in subdomains, such as mgt.company.local (our management servers). Our Windows servers live mostly in office.company.local, but some of them live in .mgt.company.local and .customers.company.local. The 2003 servers all succesfully authenticate against company.local as the Windows domain. Their position in the infrastructure is set by setting the primary DNS suffix under the network settings and the computer name dialog. Trying to do the same with a brand new 2008 install throws an error though: "Changing the Primary Domain DNS name of this computer to office.company.local failed [...] The specified server cannot perform the requested operation" I tried googling, but the closest I came was the Technet article on DNS Devolution, and I can't make heads nor tails on how to apply that to my case. Addendum 2012-10-23: The problem is not joining the domain, that works, the problem is that it joins with the wrong name, as .company.local, instead of .office.company.local. So far everything works, but I'm rather afraid to run production like this, because sooner or later something is going to complain about the AD name not matching DNS.

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  • Internet keeps connecting and disconnecting

    - by OmerPT
    I have a PC running 32bit Windows 7 Professional. My wireless internet card is Edimax EW-7128G, it is inside my computer case and it is connected to an antenna. My problem is: I have a wireless connection to my router, the signal is fine and it's not slow or anything, but it just keeps disconnecting every 30 seconds or so, then connects back, then it disconnects, then connects back and so on. This is new - it only started about a week ago, everything worked just fine until then. I know it's not a problem with the router because: Other computers can connect to it easily and they work just fine, no disconnections (My phone too). I know it's not a problem with the computer or the wireless card itself because: I have Ubuntu installed side-by-side with my Windows, and when I switch to Ubuntu the internet works great. This caused me to think it's probably a problem with the wireless card drivers installed on windows (Ubuntu auto-installed them, I installed them manually on windows): I tried uninstalling them, and then installing them back again, sadly that didn't help. I'm kind of lost here - can anyone think of anything else I should try? Thanks :)

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  • Windows 7 constantly accessing hard drive [duplicate]

    - by Zohar
    Possible Duplicate: Tool which finds which process is causing the heavy hard drive activity? Did you notice that on Windows 7 (I use 64-bit) the hard drive LED is constantly blinking, which means that the OS is constantly wearing the hard drive by accessing it? It's something related to the system process, and it even occurs in safe mode, so I don't think it's a third party software problem. Has anyone experienced this problem as well, and is it a Windows problem, or caused by something else? Edit: My indexing service is reduced to indexing only the Start Menu. Even if it was set for the whole computer, it would eventually stop; that's not it. My friends also suffer from the same problem. Please answer my first question: have any of you have seen a Windows 7 machine whose hard drive LED is at rest? I'm also trying to track down the offending process using procmon and Resource Monitor, and it actually seems like a system process. It could also be svchost.exe, and I'm not sure which file they are accessing since I see a lot of activity which I can't make sense of. It's loading system DLLs, accessing registry keys, and other nonsense.

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  • SQL SERVER – Enumerations in Relational Database – Best Practice

    - by pinaldave
    Marko Parkkola This article has been submitted by Marko Parkkola, Data systems designer at Saarionen Oy, Finland. Marko is excellent developer and always thinking at next level. You can read his earlier comment which created very interesting discussion here: SQL SERVER- IF EXISTS(Select null from table) vs IF EXISTS(Select 1 from table). I must express my special thanks to Marko for sending this best practice for Enumerations in Relational Database. He has really wrote excellent piece here and welcome comments here. Enumerations in Relational Database This is a subject which is very basic thing in relational databases but often not very well understood and sometimes badly implemented. There are of course many ways to do this but I concentrate only two cases, one which is “the right way” and one which is definitely wrong way. The concept Let’s say we have table Person in our database. Person has properties/fields like Firstname, Lastname, Birthday and so on. Then there’s a field that tells person’s marital status and let’s name it the same way; MaritalStatus. Now MaritalStatus is an enumeration. In C# I would definitely make it an enumeration with values likes Single, InRelationship, Married, Divorced. Now here comes the problem, SQL doesn’t have enumerations. The wrong way This is, in my opinion, absolutely the wrong way to do this. It has one upside though; you’ll see the enumeration’s description instantly when you do simple SELECT query and you don’t have to deal with mysterious values. There’s plenty of downsides too and one would be database fragmentation. Consider this (I’ve left all indexes and constraints out of the query on purpose). CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] NVARCHAR(10) ) You have nvarchar(20) field in the table that tells the marital status. Obvious problem with this is that what if you create a new value which doesn’t fit into 20 characters? You’ll have to come and alter the table. There are other problems also but I’ll leave those for the reader to think about. The correct way Here’s how I’ve done this in many projects. This model still has one problem but it can be alleviated in the application layer or with CHECK constraints if you like. First I will create a namespace table which tells the name of the enumeration. I will add one row to it too. I’ll write all the indexes and constraints here too. CREATE TABLE [CodeNamespace] ( [Id] INT IDENTITY(1, 1), [Name] NVARCHAR(100) NOT NULL, CONSTRAINT [PK_CodeNamespace] PRIMARY KEY ([Id]), CONSTRAINT [IXQ_CodeNamespace_Name] UNIQUE NONCLUSTERED ([Name]) ) GO INSERT INTO [CodeNamespace] SELECT 'MaritalStatus' GO Then I create a table that holds the actual values and which reference to namespace table in order to group the values under different namespaces. I’ll add couple of rows here too. CREATE TABLE [CodeValue] ( [CodeNamespaceId] INT NOT NULL, [Value] INT NOT NULL, [Description] NVARCHAR(100) NOT NULL, [OrderBy] INT, CONSTRAINT [PK_CodeValue] PRIMARY KEY CLUSTERED ([CodeNamespaceId], [Value]), CONSTRAINT [FK_CodeValue_CodeNamespace] FOREIGN KEY ([CodeNamespaceId]) REFERENCES [CodeNamespace] ([Id]) ) GO -- 1 is the 'MaritalStatus' namespace INSERT INTO [CodeValue] SELECT 1, 1, 'Single', 1 INSERT INTO [CodeValue] SELECT 1, 2, 'In relationship', 2 INSERT INTO [CodeValue] SELECT 1, 3, 'Married', 3 INSERT INTO [CodeValue] SELECT 1, 4, 'Divorced', 4 GO Now there’s four columns in CodeValue table. CodeNamespaceId tells under which namespace values belongs to. Value tells the enumeration value which is used in Person table (I’ll show how this is done below). Description tells what the value means. You can use this, for example, column in UI’s combo box. OrderBy tells if the values needs to be ordered in some way when displayed in the UI. And here’s the Person table again now with correct columns. I’ll add one row here to show how enumerations are to be used. CREATE TABLE [dbo].[Person] ( [Firstname] NVARCHAR(100), [Lastname] NVARCHAR(100), [Birthday] datetime, [MaritalStatus] INT ) GO INSERT INTO [Person] SELECT 'Marko', 'Parkkola', '1977-03-04', 3 GO Now I said earlier that there is one problem with this. MaritalStatus column doesn’t have any database enforced relationship to the CodeValue table so you can enter any value you like into this field. I’ve solved this problem in the application layer by selecting all the values from the CodeValue table and put them into a combobox / dropdownlist (with Value field as value and Description as text) so the end user can’t enter any illegal values; and of course I’ll check the entered value in data access layer also. I said in the “The wrong way” section that there is one benefit to it. In fact, you can have the same benefit here by using a simple view, which I schema bound so you can even index it if you like. CREATE VIEW [dbo].[Person_v] WITH SCHEMABINDING AS SELECT p.[Firstname], p.[Lastname], p.[BirthDay], c.[Description] MaritalStatus FROM [dbo].[Person] p JOIN [dbo].[CodeValue] c ON p.[MaritalStatus] = c.[Value] JOIN [dbo].[CodeNamespace] n ON n.[Id] = c.[CodeNamespaceId] AND n.[Name] = 'MaritalStatus' GO -- Select from View SELECT * FROM [dbo].[Person_v] GO This is excellent write up byMarko Parkkola. Do you have this kind of design setup at your organization? Let us know your opinion. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Best Practices, Database, DBA, Readers Contribution, Software Development, SQL, SQL Authority, SQL Documentation, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Inheritance Mapping Strategies with Entity Framework Code First CTP5: Part 3 – Table per Concrete Type (TPC) and Choosing Strategy Guidelines

    - by mortezam
    This is the third (and last) post in a series that explains different approaches to map an inheritance hierarchy with EF Code First. I've described these strategies in previous posts: Part 1 – Table per Hierarchy (TPH) Part 2 – Table per Type (TPT)In today’s blog post I am going to discuss Table per Concrete Type (TPC) which completes the inheritance mapping strategies supported by EF Code First. At the end of this post I will provide some guidelines to choose an inheritance strategy mainly based on what we've learned in this series. TPC and Entity Framework in the Past Table per Concrete type is somehow the simplest approach suggested, yet using TPC with EF is one of those concepts that has not been covered very well so far and I've seen in some resources that it was even discouraged. The reason for that is just because Entity Data Model Designer in VS2010 doesn't support TPC (even though the EF runtime does). That basically means if you are following EF's Database-First or Model-First approaches then configuring TPC requires manually writing XML in the EDMX file which is not considered to be a fun practice. Well, no more. You'll see that with Code First, creating TPC is perfectly possible with fluent API just like other strategies and you don't need to avoid TPC due to the lack of designer support as you would probably do in other EF approaches. Table per Concrete Type (TPC)In Table per Concrete type (aka Table per Concrete class) we use exactly one table for each (nonabstract) class. All properties of a class, including inherited properties, can be mapped to columns of this table, as shown in the following figure: As you can see, the SQL schema is not aware of the inheritance; effectively, we’ve mapped two unrelated tables to a more expressive class structure. If the base class was concrete, then an additional table would be needed to hold instances of that class. I have to emphasize that there is no relationship between the database tables, except for the fact that they share some similar columns. TPC Implementation in Code First Just like the TPT implementation, we need to specify a separate table for each of the subclasses. We also need to tell Code First that we want all of the inherited properties to be mapped as part of this table. In CTP5, there is a new helper method on EntityMappingConfiguration class called MapInheritedProperties that exactly does this for us. Here is the complete object model as well as the fluent API to create a TPC mapping: public abstract class BillingDetail {     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } }          public class BankAccount : BillingDetail {     public string BankName { get; set; }     public string Swift { get; set; } }          public class CreditCard : BillingDetail {     public int CardType { get; set; }     public string ExpiryMonth { get; set; }     public string ExpiryYear { get; set; } }      public class InheritanceMappingContext : DbContext {     public DbSet<BillingDetail> BillingDetails { get; set; }              protected override void OnModelCreating(ModelBuilder modelBuilder)     {         modelBuilder.Entity<BankAccount>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("BankAccounts");         });         modelBuilder.Entity<CreditCard>().Map(m =>         {             m.MapInheritedProperties();             m.ToTable("CreditCards");         });                 } } The Importance of EntityMappingConfiguration ClassAs a side note, it worth mentioning that EntityMappingConfiguration class turns out to be a key type for inheritance mapping in Code First. Here is an snapshot of this class: namespace System.Data.Entity.ModelConfiguration.Configuration.Mapping {     public class EntityMappingConfiguration<TEntityType> where TEntityType : class     {         public ValueConditionConfiguration Requires(string discriminator);         public void ToTable(string tableName);         public void MapInheritedProperties();     } } As you have seen so far, we used its Requires method to customize TPH. We also used its ToTable method to create a TPT and now we are using its MapInheritedProperties along with ToTable method to create our TPC mapping. TPC Configuration is Not Done Yet!We are not quite done with our TPC configuration and there is more into this story even though the fluent API we saw perfectly created a TPC mapping for us in the database. To see why, let's start working with our object model. For example, the following code creates two new objects of BankAccount and CreditCard types and tries to add them to the database: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount();     CreditCard creditCard = new CreditCard() { CardType = 1 };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Running this code throws an InvalidOperationException with this message: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: AcceptChanges cannot continue because the object's key values conflict with another object in the ObjectStateManager. Make sure that the key values are unique before calling AcceptChanges. The reason we got this exception is because DbContext.SaveChanges() internally invokes SaveChanges method of its internal ObjectContext. ObjectContext's SaveChanges method on its turn by default calls AcceptAllChanges after it has performed the database modifications. AcceptAllChanges method merely iterates over all entries in ObjectStateManager and invokes AcceptChanges on each of them. Since the entities are in Added state, AcceptChanges method replaces their temporary EntityKey with a regular EntityKey based on the primary key values (i.e. BillingDetailId) that come back from the database and that's where the problem occurs since both the entities have been assigned the same value for their primary key by the database (i.e. on both BillingDetailId = 1) and the problem is that ObjectStateManager cannot track objects of the same type (i.e. BillingDetail) with the same EntityKey value hence it throws. If you take a closer look at the TPC's SQL schema above, you'll see why the database generated the same values for the primary keys: the BillingDetailId column in both BankAccounts and CreditCards table has been marked as identity. How to Solve The Identity Problem in TPC As you saw, using SQL Server’s int identity columns doesn't work very well together with TPC since there will be duplicate entity keys when inserting in subclasses tables with all having the same identity seed. Therefore, to solve this, either a spread seed (where each table has its own initial seed value) will be needed, or a mechanism other than SQL Server’s int identity should be used. Some other RDBMSes have other mechanisms allowing a sequence (identity) to be shared by multiple tables, and something similar can be achieved with GUID keys in SQL Server. While using GUID keys, or int identity keys with different starting seeds will solve the problem but yet another solution would be to completely switch off identity on the primary key property. As a result, we need to take the responsibility of providing unique keys when inserting records to the database. We will go with this solution since it works regardless of which database engine is used. Switching Off Identity in Code First We can switch off identity simply by placing DatabaseGenerated attribute on the primary key property and pass DatabaseGenerationOption.None to its constructor. DatabaseGenerated attribute is a new data annotation which has been added to System.ComponentModel.DataAnnotations namespace in CTP5: public abstract class BillingDetail {     [DatabaseGenerated(DatabaseGenerationOption.None)]     public int BillingDetailId { get; set; }     public string Owner { get; set; }     public string Number { get; set; } } As always, we can achieve the same result by using fluent API, if you prefer that: modelBuilder.Entity<BillingDetail>()             .Property(p => p.BillingDetailId)             .HasDatabaseGenerationOption(DatabaseGenerationOption.None); Working With The Object Model Our TPC mapping is ready and we can try adding new records to the database. But, like I said, now we need to take care of providing unique keys when creating new objects: using (var context = new InheritanceMappingContext()) {     BankAccount bankAccount = new BankAccount()      {          BillingDetailId = 1                          };     CreditCard creditCard = new CreditCard()      {          BillingDetailId = 2,         CardType = 1     };                      context.BillingDetails.Add(bankAccount);     context.BillingDetails.Add(creditCard);     context.SaveChanges(); } Polymorphic Associations with TPC is Problematic The main problem with this approach is that it doesn’t support Polymorphic Associations very well. After all, in the database, associations are represented as foreign key relationships and in TPC, the subclasses are all mapped to different tables so a polymorphic association to their base class (abstract BillingDetail in our example) cannot be represented as a simple foreign key relationship. For example, consider the the domain model we introduced here where User has a polymorphic association with BillingDetail. This would be problematic in our TPC Schema, because if User has a many-to-one relationship with BillingDetail, the Users table would need a single foreign key column, which would have to refer both concrete subclass tables. This isn’t possible with regular foreign key constraints. Schema Evolution with TPC is Complex A further conceptual problem with this mapping strategy is that several different columns, of different tables, share exactly the same semantics. This makes schema evolution more complex. For example, a change to a base class property results in changes to multiple columns. It also makes it much more difficult to implement database integrity constraints that apply to all subclasses. Generated SQLLet's examine SQL output for polymorphic queries in TPC mapping. For example, consider this polymorphic query for all BillingDetails and the resulting SQL statements that being executed in the database: var query = from b in context.BillingDetails select b; Just like the SQL query generated by TPT mapping, the CASE statements that you see in the beginning of the query is merely to ensure columns that are irrelevant for a particular row have NULL values in the returning flattened table. (e.g. BankName for a row that represents a CreditCard type). TPC's SQL Queries are Union Based As you can see in the above screenshot, the first SELECT uses a FROM-clause subquery (which is selected with a red rectangle) to retrieve all instances of BillingDetails from all concrete class tables. The tables are combined with a UNION operator, and a literal (in this case, 0 and 1) is inserted into the intermediate result; (look at the lines highlighted in yellow.) EF reads this to instantiate the correct class given the data from a particular row. A union requires that the queries that are combined, project over the same columns; hence, EF has to pad and fill up nonexistent columns with NULL. This query will really perform well since here we can let the database optimizer find the best execution plan to combine rows from several tables. There is also no Joins involved so it has a better performance than the SQL queries generated by TPT where a Join is required between the base and subclasses tables. Choosing Strategy GuidelinesBefore we get into this discussion, I want to emphasize that there is no one single "best strategy fits all scenarios" exists. As you saw, each of the approaches have their own advantages and drawbacks. Here are some rules of thumb to identify the best strategy in a particular scenario: If you don’t require polymorphic associations or queries, lean toward TPC—in other words, if you never or rarely query for BillingDetails and you have no class that has an association to BillingDetail base class. I recommend TPC (only) for the top level of your class hierarchy, where polymorphism isn’t usually required, and when modification of the base class in the future is unlikely. If you do require polymorphic associations or queries, and subclasses declare relatively few properties (particularly if the main difference between subclasses is in their behavior), lean toward TPH. Your goal is to minimize the number of nullable columns and to convince yourself (and your DBA) that a denormalized schema won’t create problems in the long run. If you do require polymorphic associations or queries, and subclasses declare many properties (subclasses differ mainly by the data they hold), lean toward TPT. Or, depending on the width and depth of your inheritance hierarchy and the possible cost of joins versus unions, use TPC. By default, choose TPH only for simple problems. For more complex cases (or when you’re overruled by a data modeler insisting on the importance of nullability constraints and normalization), you should consider the TPT strategy. But at that point, ask yourself whether it may not be better to remodel inheritance as delegation in the object model (delegation is a way of making composition as powerful for reuse as inheritance). Complex inheritance is often best avoided for all sorts of reasons unrelated to persistence or ORM. EF acts as a buffer between the domain and relational models, but that doesn’t mean you can ignore persistence concerns when designing your classes. SummaryIn this series, we focused on one of the main structural aspect of the object/relational paradigm mismatch which is inheritance and discussed how EF solve this problem as an ORM solution. We learned about the three well-known inheritance mapping strategies and their implementations in EF Code First. Hopefully it gives you a better insight about the mapping of inheritance hierarchies as well as choosing the best strategy for your particular scenario. Happy New Year and Happy Code-Firsting! References ADO.NET team blog Java Persistence with Hibernate book a { color: #5A99FF; } a:visited { color: #5A99FF; } .title { padding-bottom: 5px; font-family: Segoe UI; font-size: 11pt; font-weight: bold; padding-top: 15px; } .code, .typeName { font-family: consolas; } .typeName { color: #2b91af; } .padTop5 { padding-top: 5px; } .padTop10 { padding-top: 10px; } .exception { background-color: #f0f0f0; font-style: italic; padding-bottom: 5px; padding-left: 5px; padding-top: 5px; padding-right: 5px; }

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  • Request Limit Length Limits for IIS&rsquo;s requestFiltering Module

    - by Rick Strahl
    Today I updated my CodePaste.net site to MVC 3 and pushed an update to the site. The update of MVC went pretty smooth as well as most of the update process to the live site. Short of missing a web.config change in the /views folder that caused blank pages on the server, the process was relatively painless. However, one issue that kicked my ass for about an hour – and not foe the first time – was a problem with my OpenId authentication using DotNetOpenAuth. I tested the site operation fairly extensively locally and everything worked no problem, but on the server the OpenId returns resulted in a 404 response from IIS for a nice friendly OpenId return URL like this: http://codepaste.net/Account/OpenIdLogon?dnoa.userSuppliedIdentifier=http%3A%2F%2Frstrahl.myopenid.com%2F&dnoa.return_to_sig_handle=%7B634239223364590000%7D%7BjbHzkg%3D%3D%7D&dnoa.return_to_sig=7%2BcGhp7UUkcV2B8W29ibIDnZuoGoqzyS%2F%2FbF%2FhhYscgWzjg%2BB%2Fj10ZpNdBkUCu86dkTL6f4OK2zY5qHhCnJ2Dw%3D%3D&openid.assoc_handle=%7BHMAC-SHA256%7D%7B4cca49b2%7D%7BMVGByQ%3D%3D%7D&openid.claimed_id=http%3A%2F%2Frstrahl.myopenid.com%2F&openid.identity=http%3A%2F%2Frstrahl.myopenid.com%2F&openid.mode=id_res&openid.ns=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0&openid.ns.sreg=http%3A%2F%2Fopenid.net%2Fextensions%2Fsreg%2F1.1&openid.op_endpoint=http%3A%2F%2Fwww.myopenid.com%2Fserver&openid.response_nonce=2010-10-29T04%3A12%3A53Zn5F4r5&openid.return_to=http%3A%2F%2Fcodepaste.net%2FAccount%2FOpenIdLogon%3Fdnoa.userSuppliedIdentifier%3Dhttp%253A%252F%252Frstrahl.myopenid.com%252F%26dnoa.return_to_sig_handle%3D%257B634239223364590000%257D%257BjbHzkg%253D%253D%257D%26dnoa.return_to_sig%3D7%252BcGhp7UUkcV2B8W29ibIDnZuoGoqzyS%252F%252FbF%252FhhYscgWzjg%252BB%252Fj10ZpNdBkUCu86dkTL6f4OK2zY5qHhCnJ2Dw%253D%253D&openid.sig=h1GCSBTDAn1on98sLA6cti%2Bj1M6RffNerdVEI80mnYE%3D&openid.signed=assoc_handle%2Cclaimed_id%2Cidentity%2Cmode%2Cns%2Cns.sreg%2Cop_endpoint%2Cresponse_nonce%2Creturn_to%2Csigned%2Csreg.email%2Csreg.fullname&openid.sreg.email=rstrahl%40host.com&openid.sreg.fullname=Rick+Strahl A 404 of course isn’t terribly helpful – normally a 404 is a resource not found error, but the resource is definitely there. So how the heck do you figure out what’s wrong? If you’re just interested in the solution, here’s the short version: IIS by default allows only for a 1024 byte query string, which is obviously exceeded by the above. The setting is controlled by the RequestFiltering module in IIS 6 and later which can be configured in ApplicationHost.config (in \%windir\system32\inetsvr\config). To set the value configure the requestLimits key like so: <configuration> <security> <requestFiltering> <requestLimits maxQueryString="2048"> </requestLimits> </requestFiltering> </security> </configuration> This fixed me right up and made the requests work. How do you find out about problems like this? Ah yes the troubles of an administrator? Read on and I’ll take you through a quick review of how I tracked this down. Finding the Problem The issue with the error returned is that IIS returns a 404 Resource not found error and doesn’t provide much information about it. If you’re lucky enough to be able to run your site from the localhost IIS is actually very helpful and gives you the right information immediately in a nicely detailed error page. The bottom of the page actually describes exactly what needs to be fixed. One problem with this easy way to find an error: You HAVE TO run localhost. On my server which has about 10 domains running localhost doesn’t point at the particular site I had problems with so I didn’t get the luxury of this nice error page. Using Failed Request Tracing to retrieve Error Info The first place I go with IIS errors is to turn on Failed Request Tracing in IIS to get more error information. If you have access to the server to make a configuration change you can enable Failed Request Tracing like this: Find the Failed Request Tracing Rules in the IIS Service Manager.   Select the option and then Edit Site Tracing to enable tracing. Then add a rule for * (all content) and specify status codes from 100-999 to capture all errors. if you know exactly what error you’re looking for it might help to specify it exactly to keep the number of errors down. Then run your request and let it fail. IIS will throw error log files into a folder like this C:\inetpub\logs\FailedReqLogFiles\W3SVC5 where the last 5 is the instance ID of the site. These files are XML but they include an XSL stylesheet that provides some decent formatting. In this case it pointed me straight at the offending module:   Ok, it’s the RequestFilteringModule. Request Filtering is built into IIS 6-7 and configured in ApplicationHost.config. This module defines a few basic rules about what paths and extensions are allowed in requests and among other things how long a query string is allowed to be. Most of these settings are pretty sensible but the query string value can easily become a problem especially if you’re dealing with OpenId since these return URLs are quite extensive. Debugging failed requests is never fun, but IIS 6 and forward at least provides us the tools that can help us point in the right direction. The error message the FRT report isn’t as nice as the IIS error message but it at least points at the offending module which gave me the clue I needed to look at request restrictions in ApplicationHost.config. This would still be a stretch if you’re not intimately familiar, but I think with some Google searches it would be easy to track this down with a few tries… Hope this was useful to some of you. Useful to me to put this out as a reminder – I’ve run into this issue before myself and totally forgot. Next time I got it, right?© Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  Security  

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  • Aamir Khan’s Satyamev Jayate stirs a movement

    - by Gopinath
    Bollywood actor Aamir Khan is known for his dedication and hard work in inspiring millions of viewers though movies by discussing social problems and motivating people to solve them. His movie Rang De Basanthi seeded Indian anti-corruption movement, Tare Zameen Par touched the problems faced by few challenged kids and the latest movie 3 idiots exposed how education institutions in India are producing lakhs of Donkeys out of colleges every year. He extended his dedication of serving the society to small screen with the launch of reality TV show Satyamev Jayate. Before you start misjudging it as one of those non sense drama / entertaining reality shows, let me tell you that it is not a typical music, games, fight or dance reality show. Satyamev Jayate is all about the real people of India, their problems and how to tackle them.  This is not just a reality show, its movement to educate people about the social evils. Its been many years since I spent couple of hours  in front of TV as most of the programs are too cynical or does not add much value.  In my childhood I use to anxiously wait for Mahabarath or He-Man TV shows to start but after a two decades I waited anxiously for the start of Satyamev Jayate. The wait was worth and the 1 hours 30 minutes spent watching it meaningful. When was the last time you were so satisfied after watching a TV show and inspired to do something? I don’t remember. Today, the show focused on female foeticide and its impact. It showed women who were tortured and forced to abort female foetuses. On the show few brave women shared their experiences of giving birth to girl babies and rough times they are going through with their in-laws & husbands. The show not only focused on the problem but also on the root cause of the evil,  inspiring people working to tackle it and what every individual can do his part to solve it.  The best part of the show is,  its not a blame game. When there is a problem most of the people quickly get into identifying who is wrong and start blaming them instead of solve the actual problem.  Aamir did not blame anyone for female foeticide – neither the government who don’t impose strict rules, nor the doctors who abort girl babies to make money or the mother-in-laws & husbands who torcher girl baby mothers are blamed. He careful highlighted the problem, showed horrifying statistics and their impact on the future society and few inspiring people working to tackle the problem.  He touched heart and stirred a movement against the issue. First time ever I voted for a reality show through SMS and it’s for Satyamev Jayate. I’m proud to do so. Here are the few reactions of popular people, activists & media about the program @aamir_khan absolutely the best program I have seen on TV in recent past. Thanku for converting an idiot box into an inspirationsl medium — Kiran Bedi (@thekiranbedi) May 6, 2012 Satyamev Jayate proves tht TV 2 can b a tool of social change. — Shekhar Kapur (@shekharkapur) May 6, 2012 i absolutely loved #satyamevjayate. at least aamir is doing what all of us only talk about. — Harsha Bhogle (@bhogleharsha) May 6, 2012 Now Television will no longer be called an idiot box,the VISION of Television broadens up with#SatyamevJayate !!! — Madhur Bhandarkar (@mbhandarkar268) May 6, 2012 The Sunday 11am slot seems to have come back with a bang… #SatyamevJayate — atul kasbekar (@atulkasbekar) May 6, 2012   I was spellbound, says Prasoon Joshi – It’s a unique show. I was completely bowled over by it. It’s a never-done before concept Aamir Khan strikes the right chord with Satyamev Jayate – The format is quite crisp. Talking about the emotional connect, there are moments when your eyes well up with tears, but the various segments ensure there’s more content than emotional drama ‘Satyamev Jayate’ gutsy, sensible show: Viewers – From filmmakers to clinical psychologists to professors – everyone has given the thumbs up to Aamir Khan’s television show ‘Satyamev Jayate’, saying it is a gutsy, hard-hitting and sensible programme that strikes an emotional chord with the audiences. Aamir Khan’s TV debut ‘Satyamev Jayate’ takes Twitter by storm – The roads of the capital sported a deserted look around 11 am on Sunday morning, as everyone was hooked on to their TV sets. Did you watch the program? What is your opinion? I’m waiting for next 11 AM of next Sunday. Are you?

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  • Understanding each other in web development

    - by Pete Hotchkin
    During my career I have been lucky enough to work in several different roles within web development with many extremely talented people, from incredible designers who were passionate about the placement of every pixel right through to server administrators and DBAs who were always measuring the improvements they were making to their queries in the smallest possible unit. The problem I always faced was that more often than not I was stuck in the middle trying to mediate between these different functions and enable each side to understand the other’s point of view. The main areas of contention that there have always been between these functional groups in my experience have been at 2 key points: during the build phase and then when there is a problem post-build. During both of these times it is often easier for someone to pass the buck onto someone else than spend the time to understand the other person’s perspective. Below is a quick look at two upcoming tools that will not only speed up the build phase for each function, but  also help when it comes to the issues faced once a site has been pushed live. In my experience a web project goes through several phases of development. The first of these is design, generally handled as Photoshop files which are then passed onto a front-end developer. This is the first point at which heated discussions can arise. One problem I’ve seen several times is that the designer doesn’t fully understand the platform constraints that need to be considered, and as a result has designed something that does not translate very well or is simply not possible. Working at Red Gate, I am lucky enough to be able to meet some amazing people and this happened just the other day when I was introduced to Neil Kinnish and Pete Nelson, the creators of what I believe could be a great asset in this designer-developer relationship, Mixture. Mixture allows the front end developer to quickly prototype a web page with built-in frameworks such as bootstrap. It’s not an IDE however, it just sits there in the background and monitors the project files in the background so every time you save a file from your favorite IDE, it will compile things like LESS, compact your JavaScript and the automatically refresh your test browser so you can see the changes instantly. I think one of the best parts of this however is a single button that pushes the changed files up to the web so the designer can instantly see how far the developer has got and the problem that he is facing at that time without the need to spend time setting up a remote server. I can see this being a real asset to remote teams where there needs to be a compromise between the designer and the front-end developer, or just to allow the designer to see how the build is progressing and suggest small alterations. Once the design has been built into the front end the designer’s job is generally done and there are no other points of contention between the designer and the other functions involved in building these web projects. As the project moves into the stage of integrating it into the back end and deploying it to the production server other functions start to be pulled in and other issues arise such as the back-end developer understanding the frameworks that they are using such as the routes that are in place in an MVC application or the number of database calls that the ORM layer is actually making. There are many tools out there that can actually help with these problems such as mini profiler that gives you a quick snapshot of what is going on directly in the browser. For a slightly more in-depth look at what is happening and to gain a deeper understanding of an application you may be working on though, you may want to consider Glimpse. Created by Nik and Anthony, it is an application that sits at the bottom of your browser (installed via NuGet) which can show you information about how your application is pieced together and how the information on screen is being delivered as it happens. With a wealth of community-built plugins such as one for nHibernate and linq2SQL (full list of plugins on NuGet). It can be customized directly to your own setup to truly delve into the code to see what is happening, and can help to reduce the number of confusing moments about whether it is your code that is going wrong or whether there is something more sinister happening directly on the server. All the tools that I have mentioned in this post help to do one thing above all, and that is to ease the barrier of understanding between the different functions that are involved in building and maintaining a web application. In my experience it is very easy to say “Well, that’s not my problem”, simply because the two functions involved don’t truly understand the other’s point of view. Software should not only be seen as a way to streamline our own working process or as a debugging tool but also a communication aid to improve the entire lifecycle of a web project. Glimpse is actually the project that I am the designer on and I would love to get your feedback if you do decide to try it out or if you would like to share your own experiences of working on web projects please fill in your details at https://www.surveymk.com/s/joinGlimpse  or add a comment below and I will get in touch with you.

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  • Pain Comes Instantly

    - by user701213
    When I look back at recent blog entries – many of which are not all that current (more on where my available writing time is going later) – I am struck by how many of them focus on public policy or legislative issues instead of, say, the latest nefarious cyberattack or exploit (or everyone’s favorite new pastime: coining terms for the Coming Cyberpocalypse: “digital Pearl Harbor” is so 1941). Speaking of which, I personally hope evil hackers from Malefactoria will someday hack into my bathroom scale – which in a future time will be connected to the Internet because, gosh, wouldn’t it be great to have absolutely everything in your life Internet-enabled? – and recalibrate it so I’m 10 pounds thinner. The horror. In part, my focus on public policy is due to an admitted limitation of my skill set. I enjoy reading technical articles about exploits and cybersecurity trends, but writing a blog entry on those topics would take more research than I have time for and, quite honestly, doesn’t play to my strengths. The first rule of writing is “write what you know.” The bigger contributing factor to my recent paucity of blog entries is that more and more of my waking hours are spent engaging in “thrust and parry” activity involving emerging regulations of some sort or other. I’ve opined in earlier blogs about what constitutes good and reasonable public policy so nobody can accuse me of being reflexively anti-regulation. That said, you have so many cycles in the day, and most of us would rather spend it slaying actual dragons than participating in focus groups on whether dragons are really a problem, whether lassoing them (with organic, sustainable and recyclable lassos) is preferable to slaying them – after all, dragons are people, too - and whether we need lasso compliance auditors to make sure lassos are being used correctly and humanely. (A point that seems to evade many rule makers: slaying dragons actually accomplishes something, whereas talking about “approved dragon slaying procedures and requirements” wastes the time of those who are competent to dispatch actual dragons and who were doing so very well without the input of “dragon-slaying theorists.”) Unfortunately for so many of us who would just get on with doing our day jobs, cybersecurity is rapidly devolving into the “focus groups on dragon dispatching” realm, which actual dragons slayers have little choice but to participate in. The general trend in cybersecurity is that powers-that-be – which encompasses groups other than just legislators – are often increasingly concerned and therefore feel they need to Do Something About Cybersecurity. Many seem to believe that if only we had the right amount of regulation and oversight, there would be no data breaches: a breach simply must mean Someone Is At Fault and Needs Supervision. (Leaving aside the fact that we have lots of home invasions despite a) guard dogs b) liberal carry permits c) alarm systems d) etc.) Also note that many well-managed and security-aware organizations, like the US Department of Defense, still get hacked. More specifically, many powers-that-be feel they must direct industry in a multiplicity of ways, up to and including how we actually build and deploy information technology systems. The more prescriptive the requirement, the more regulators or overseers a) can be seen to be doing something b) feel as if they are doing something regardless of whether they are actually doing something useful or cost effective. Note: an unfortunate concomitant of Doing Something is that often the cure is worse than the ailment. That is, doing what overseers want creates unfortunate byproducts that they either didn’t foresee or worse, don’t care about. After all, the logic goes, we Did Something. Prescriptive practice in the IT industry is problematic for a number of reasons. For a start, prescriptive guidance is really only appropriate if: • It is cost effective• It is “current” (meaning, the guidance doesn’t require the use of the technical equivalent of buggy whips long after horse-drawn transportation has become passé)*• It is practical (that is, pragmatic, proven and effective in the real world, not theoretical and unproven)• It solves the right problem With the above in mind, heading up the list of “you must be joking” regulations are recent disturbing developments in the Payment Card Industry (PCI) world. I’d like to give PCI kahunas the benefit of the doubt about their intentions, except that efforts by Oracle among others to make them aware of “unfortunate side effects of your requirements” – which is as tactful I can be for reasons that I believe will become obvious below - have gone, to-date, unanswered and more importantly, unchanged. A little background on PCI before I get too wound up. In 2008, the Payment Card Industry (PCI) Security Standards Council (SSC) introduced the Payment Application Data Security Standard (PA-DSS). That standard requires vendors of payment applications to ensure that their products implement specific requirements and undergo security assessment procedures. In order to have an application listed as a Validated Payment Application (VPA) and available for use by merchants, software vendors are required to execute the PCI Payment Application Vendor Release Agreement (VRA). (Are you still with me through all the acronyms?) Beginning in August 2010, the VRA imposed new obligations on vendors that are extraordinary and extraordinarily bad, short-sighted and unworkable. Specifically, PCI requires vendors to disclose (dare we say “tell all?”) to PCI any known security vulnerabilities and associated security breaches involving VPAs. ASAP. Think about the impact of that. PCI is asking a vendor to disclose to them: • Specific details of security vulnerabilities • Including exploit information or technical details of the vulnerability • Whether or not there is any mitigation available (as in a patch) PCI, in turn, has the right to blab about any and all of the above – specifically, to distribute all the gory details of what is disclosed - to the PCI SSC, qualified security assessors (QSAs), and any affiliate or agent or adviser of those entities, who are in turn permitted to share it with their respective affiliates, agents, employees, contractors, merchants, processors, service providers and other business partners. This assorted crew can’t be more than, oh, hundreds of thousands of entities. Does anybody believe that several hundred thousand people can keep a secret? Or that several hundred thousand people are all equally trustworthy? Or that not one of the people getting all that information would blab vulnerability details to a bad guy, even by accident? Or be a bad guy who uses the information to break into systems? (Wait, was that the Easter Bunny that just hopped by? Bringing world peace, no doubt.) Sarcasm aside, common sense tells us that telling lots of people a secret is guaranteed to “unsecret” the secret. Notably, being provided details of a vulnerability (without a patch) is of little or no use to companies running the affected application. Few users have the technological sophistication to create a workaround, and even if they do, most workarounds break some other functionality in the application or surrounding environment. Also, given the differences among corporate implementations of any application, it is highly unlikely that a single workaround is going to work for all corporate users. So until a patch is developed by the vendor, users remain at risk of exploit: even more so if the details of vulnerability have been widely shared. Sharing that information widely before a patch is available therefore does not help users, and instead helps only those wanting to exploit known security bugs. There’s a shocker for you. Furthermore, we already know that insider information about security vulnerabilities inevitably leaks, which is why most vendors closely hold such information and limit dissemination until a patch is available (and frequently limit dissemination of technical details even with the release of a patch). That’s the industry norm, not that PCI seems to realize or acknowledge that. Why would anybody release a bunch of highly technical exploit information to a cast of thousands, whose only “vetting” is that they are members of a PCI consortium? Oracle has had personal experience with this problem, which is one reason why information on security vulnerabilities at Oracle is “need to know” (we use our own row level access control to limit access to security bugs in our bug database, and thus less than 1% of development has access to this information), and we don’t provide some customers with more information than others or with vulnerability information and/or patches earlier than others. Failure to remember “insider information always leaks” creates problems in the general case, and has created problems for us specifically. A number of years ago, one of the UK intelligence agencies had information about a non-public security vulnerability in an Oracle product that they circulated among other UK and Commonwealth defense and intelligence entities. Nobody, it should be pointed out, bothered to report the problem to Oracle, even though only Oracle could produce a patch. The vulnerability was finally reported to Oracle by (drum roll) a US-based commercial company, to whom the information had leaked. (Note: every time I tell this story, the MI-whatever agency that created the problem gets a bit shirty with us. I know they meant well and have improved their vulnerability handling/sharing processes but, dudes, next time you find an Oracle vulnerability, try reporting it to us first before blabbing to lots of people who can’t actually fix the problem. Thank you!) Getting back to PCI: clearly, these new disclosure obligations increase the risk of exploitation of a vulnerability in a VPA and thus, of misappropriation of payment card data and customer information that a VPA processes, stores or transmits. It stands to reason that VRA’s current requirement for the widespread distribution of security vulnerability exploit details -- at any time, but particularly before a vendor can issue a patch or a workaround -- is very poor public policy. It effectively publicizes information of great value to potential attackers while not providing compensating benefits - actually, any benefits - to payment card merchants or consumers. In fact, it magnifies the risk to payment card merchants and consumers. The risk is most prominent in the time before a patch has been released, since customers often have little option but to continue using an application or system despite the risks. However, the risk is not limited to the time before a patch is issued: customers often need days, or weeks, to apply patches to systems, based upon the complexity of the issue and dependence on surrounding programs. Rather than decreasing the available window of exploit, this requirement increases the available window of exploit, both as to time available to exploit a vulnerability and the ease with which it can be exploited. Also, why would hackers focus on finding new vulnerabilities to exploit if they can get “EZHack” handed to them in such a manner: a) a vulnerability b) in a payment application c) with exploit code: the “Hacking Trifecta!“ It’s fair to say that this is probably the exact opposite of what PCI – or any of us – would want. Established industry practice concerning vulnerability handling avoids the risks created by the VRA’s vulnerability disclosure requirements. Specifically, the norm is not to release information about a security bug until the associated patch (or a pretty darn good workaround) has been issued. Once a patch is available, the notice to the user community is a high-level communication discussing the product at issue, the level of risk associated with the vulnerability, and how to apply the patch. The notices do not include either the specific customers affected by the vulnerability or forensic reports with maps of the exploit (both of which are required by the current VRA). In this way, customers have the tools they need to prioritize patching and to help prevent an attack, and the information released does not increase the risk of exploit. Furthermore, many vendors already use industry standards for vulnerability description: Common Vulnerability Enumeration (CVE) and Common Vulnerability Scoring System (CVSS). CVE helps ensure that customers know which particular issues a patch addresses and CVSS helps customers determine how severe a vulnerability is on a relative scale. Industry already provides the tools customers need to know what the patch contains and how bad the problem is that the patch remediates. So, what’s a poor vendor to do? Oracle is reaching out to other vendors subject to PCI and attempting to enlist then in a broad effort to engage PCI in rethinking (that is, eradicating) these requirements. I would therefore urge all who care about this issue, but especially those in the vendor community whose applications are subject to PCI and who may not have know they were being asked to tell-all to PCI and put their customers at risk, to do one of the following: • Contact PCI with your concerns• Contact Oracle (we are looking for vendors to sign our statement of concern)• And make sure you tell your customers that you have to rat them out to PCI if there is a breach involving the payment application I like to be charitable and say “PCI meant well” but in as important a public policy issue as what you disclose about vulnerabilities, to whom and when, meaning well isn’t enough. We need to do well. PCI, as regards this particular issue, has not done well, and has compounded the error by thus far being nonresponsive to those of us who have labored mightily to try to explain why they might want to rethink telling the entire planet about security problems with no solutions. By Way of Explanation… Non-related to PCI whatsoever, and the explanation for why I have not been blogging a lot recently, I have been working on Other Writing Venues with my sister Diane (who has also worked in the tech sector, inflicting upgrades on unsuspecting and largely ungrateful end users). I am pleased to note that we have recently (self-)published the first in the Miss Information Technology Murder Mystery series, Outsourcing Murder. The genre might best be described as “chick lit meets geek scene.” Our sisterly nom de plume is Maddi Davidson and (shameless plug follows): you can order the paper version of the book on Amazon, or the Kindle or Nook versions on www.amazon.com or www.bn.com, respectively. From our book jacket: Emma Jones, a 20-something IT consultant, is working on an outsourcing project at Tahiti Tacos, a restaurant chain offering Polynexican cuisine: refried poi, anyone? Emma despises her boss Padmanabh, a brilliant but arrogant partner in GD Consulting. When Emma discovers His-Royal-Padness’s body (verdict: death by cricket bat), she becomes a suspect.With her overprotective family and her best friend Stacey providing endless support and advice, Emma stumbles her way through an investigation of Padmanabh’s murder, bolstered by fusion food feeding frenzies, endless cups of frou-frou coffee and serious surfing sessions. While Stacey knows a PI who owes her a favor, landlady Magda urges Emma to tart up her underwear drawer before the next cute cop with a search warrant arrives. Emma’s mother offers to fix her up with a PhD student at Berkeley and showers her with self-defense gizmos while her old lover Keoni beckons from Hawai’i. And everyone, even Shaun the barista, knows a good lawyer. Book 2, Denial of Service, is coming out this summer. * Given the rate of change in technology, today’s “thou shalts” are easily next year’s “buggy whip guidance.”

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  • Developing Schema Compare for Oracle (Part 3): Ghost Objects

    - by Simon Cooper
    In the previous blog post, I covered how we solved the problem of dependencies between objects and between schemas. However, that isn’t the end of the issue. The dependencies algorithm I described works when you’re querying live databases and you can get dependencies for a particular schema direct from the server, and that’s all well and good. To throw a (rather large) spanner in the works, Schema Compare also has the concept of a snapshot, which is a read-only compressed XML representation of a selection of schemas that can be compared in the same way as a live database. This can be useful for keeping historical records or a baseline of a database schema, or comparing a schema on a computer that doesn’t have direct access to the database. So, how do snapshots interact with dependencies? Inter-database dependencies don't pose an issue as we store the dependencies in the snapshot. However, comparing a snapshot to a live database with cross-schema dependencies does cause a problem; what if the live database has a dependency to an object that does not exist in the snapshot? Take a basic example schema, where you’re only populating SchemaA: SOURCE   TARGET (using snapshot) CREATE TABLE SchemaA.Table1 ( Col1 NUMBER REFERENCES SchemaB.Table1(col1));   CREATE TABLE SchemaA.Table1 ( Col1 VARCHAR2(100)); CREATE TABLE SchemaB.Table1 ( Col1 NUMBER PRIMARY KEY);   CREATE TABLE SchemaB.Table1 ( Col1 VARCHAR2(100)); In this case, we want to generate a sync script to synchronize SchemaA.Table1 on the database represented by the snapshot. When taking a snapshot, database dependencies are followed, but because you’re not comparing it to anything at the time, the comparison dependencies algorithm described in my last post cannot be used. So, as you only take a snapshot of SchemaA on the target database, SchemaB.Table1 will not be in the snapshot. If this snapshot is then used to compare against the above source schema, SchemaB.Table1 will be included in the source, but the object will not be found in the target snapshot. This is the same problem that was solved with comparison dependencies, but here we cannot use the comparison dependencies algorithm as the snapshot has not got any information on SchemaB! We've now hit quite a big problem - we’re trying to include SchemaB.Table1 in the target, but we simply do not know the status of this object on the database the snapshot was taken from; whether it exists in the database at all, whether it’s the same as the target, whether it’s different... What can we do about this sorry state of affairs? Well, not a lot, it would seem. We can’t query the original database, as it may not be accessible, and we cannot assume any default state as it could be wrong and break the script (and we currently do not have a roll-back mechanism for failed synchronizes). The only way to fix this properly is for the user to go right back to the start and re-create the snapshot, explicitly including the schemas of these 'ghost' objects. So, the only thing we can do is flag up dependent ghost objects in the UI, and ask the user what we should do with it – assume it doesn’t exist, assume it’s the same as the target, or specify a definition for it. Unfortunately, such functionality didn’t make the cut for v1 of Schema Compare (as this is very much an edge case for a non-critical piece of functionality), so we simply flag the ghost objects up in the sync wizard as unsyncable, and let the user sort out what’s going on and edit the sync script as appropriate. There are some things that we do do to alleviate somewhat this rather unhappy situation; if a user creates a snapshot from the source or target of a database comparison, we include all the objects registered from the database, not just the ones in the schemas originally selected for comparison. This includes any extra dependent objects registered through the comparison dependencies algorithm. If the user then compares the resulting snapshot against the same database they were comparing against when it was created, the extra dependencies will be included in the snapshot as required and everything will be good. Fortunately, this problem will come up quite rarely, and only when the user uses snapshots and tries to sync objects with unknown cross-schema dependencies. However, the solution is not an easy one, and lead to some difficult architecture and design decisions within the product. And all this pain follows from the simple decision to allow schema pre-filtering! Next: why adding a column to a table isn't as easy as you would think...

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  • ORA-7445 Troubleshooting

    - by [email protected]
        QUICKLINK: Note 153788.1 ORA-600/ORA-7445 Lookup tool Note 1082674.1 : A Video To Demonstrate The Usage Of The ORA-600/ORA-7445 Lookup Tool [Video]   Have you observed an ORA-07445 error reported in your alert log? While the ORA-600 error is "captured" as a handled exception in the Oracle source code, the ORA-7445 is an unhandled exception error due to an OS exception which should result in the creation of a core file.  An ORA-7445 is a generic error, and can occur from anywhere in the Oracle code. The precise location of the error is identified by the core file and/or trace file it produces.  Looking for the best way to diagnose? Whenever an ORA-7445 error is raised a core file is generated.  There may be a trace file generated with the error as well.   Prior to 11g, the core files are located in the CORE_DUMP_DEST directory.   Starting with 11g, there is a new advanced fault diagnosability infrastructure to manage trace data.  Diagnostic files are written into a root directory for all diagnostic data called the ADR home.   Core files at 11g will go to the ADR HOME/cdump directory.   For more information on the Oracle 11g Diagnosability feature see Note 453125.1 11g Diagnosability Frequently Asked Questions Note 443529.1 11g Quick Steps to Package and Send Critical Error Diagnostic Information to Support[Video]   NOTE:  While the core file is captured in the Diagnosability infrastructure, the file may not be included with a diagnostic package.1.  Check the Alert LogThe alert log may indicate additional errors or other internal errors at the time of the problem.   In some cases, the ORA-7445 error will occur along with ORA-600, ORA-3113, ORA-4030 errors.  The ORA-7445 error can be side effects of the other problems and you should review the first error and associated core file or trace file and work down the list of errors.   Note 1020463.6 DIAGNOSING ORA-3113 ERRORS Note 1812.1 TECH:  Getting a Stack Trace from a CORE file Note 414966.1 RDA Documentation Index   If the ORA-7445 errors are not associated with other error conditions, ensure the trace data is not truncated. If you see a message at the end of the file   "MAX DUMP FILE SIZE EXCEEDED"   the MAX_DUMP_FILE_SIZE parameter is not setup high enough or to 'unlimited'. There could be vital diagnostic information missing in the file and discovering the root issue may be very difficult.  Set the MAX_DUMP_FILE_SIZE appropriately and regenerate the error for complete trace information. For pointers on deeper analysis of these errors see   Note 390293.1 Introduction to 600/7445 Internal Error Analysis Note 211909.1 Customer Introduction to ORA-7445 Errors 2.  Search 600/7445 Lookup Tool Visit My Oracle Support to access the ORA-00600 Lookup tool (Note 153788.1). The ORA-600/ORA-7445 Lookup tool may lead you to applicable content in My Oracle Support on the problem and can be used to investigate the problem with argument data from the error message or you can pull out key stack pointers from the associated trace file to match up against known bugs.3.  "Fine tune" searches in Knowledge Base As the ORA-7445 error indicates an unhandled exception in the Oracle source code, your search in the Oracle Knowledge Base will need to focus on the stack data from the core file or the trace file. Keep in mind that searches on generic argument data will bring back a large result set.  The more you can learn about the environment and code leading to the errors, the easier it will be to narrow the hit list to match your problem. Note 153788.1 ORA-600/ORA-7445 TroubleshooterNote 1082674.1 A Video To Demonstrate The Usage Of The ORA-600/ORA-7445 Lookup Tool [Video] NOTE:  If no trace file is captured, see Note 1812.1 TECH:  Getting a Stack Trace from a CORE file.  Core files are managed through 11g Diagnosability, but are not packaged with other diagnostic data automatically.  The core files can be quite large, but may be useful during analysis within Oracle Support.4.  If assistance is required from Oracle Should it become necessary to get assistance from Oracle Support on an ORA-7445 problem, please provide at a minimum, the Alert log  Associated tracefile(s) or incident package at 11g Patch level  information Core file(s)  Information about changes in configuration and/or application prior to  issues  If error is reproducible, a self-contained reproducible testcase: Note.232963.1 How to Build a Testcase for Oracle Data Server Support to Reproduce ORA-600 and ORA-7445 Errors RDA report or Oracle Configuration Manager information Oracle Configuration Manager Quick Start Guide Note 548815.1 My Oracle Support Configuration Management FAQ Note 414966.1 RDA Documentation Index ***For reference to the content in this blog, refer to Note.1092832.1 Master Note for Diagnosing ORA-600

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  • Becoming A Great Developer

    - by Lee Brandt
    Image via Wikipedia I’ve been doing the whole programming thing for awhile and reading and watching some of the best in the business. I have come to notice that the really great developers do a few things that (I think) makes them great. Now don’t get me wrong, I am not saying that I am one of these few. I still struggle with doing some of the things that makes one great at development. Coincidently, many of these things also make you a better person period. Believe That Guidance Is Better Than Answers This is one I have no problem with. I prefer guidance any time I am learning from another developer. Answers may get you going, but guidance will leave you stranded. At some point, you will come across a problem that can only be solved by thinking for yourself and this is where that guidance will really come in handy. You can use that guidance and extrapolate whatever technology to salve that problem (if it’s the right tool for solving that problem). The problem is, lots of developers simply want someone to tell them, “Do this, then this, then set that, and write this.” Favor thinking and learn the guidance of doing X and don’t ask someone to show you how to do X, if that makes sense. Read, Read and Read If you don’t like reading, you’re probably NOT going to make it into the Great Developer group. Great developers read books, they read magazines and they read code. Open source playgrounds like SourceForge, CodePlex and GitHub, have made it extremely easy to download code from developers you admire and see how they do stuff. Chances are, if you read their blog too, they’ll even explain WHY they did what they did (see “Guidance” above). MSDN and Code Magazine have not only code samples, but explanations of how to use certain technologies and sometimes even when NOT to use that same technology. Books are also out on just about every topic. I still favor the less technology centric books. For instance, I generally don’t buy books like, “Getting Started with Jiminy Jappets”. I look for titles like, “How To Write More Effective Code” (again, see guidance). The Addison-Wesley Signature Series is a great example of these types of books. They teach technology-agnostic concepts. Head First Design Patterns is another great guidance book. It teaches the "Gang Of Four" Design Patterns in a very easy-to-understand, picture-heavy way (I LIKE pictures). Hang Your Balls Out There Even though the advice came from a 3rd-shift Kinko’s attendant, doesn’t mean it’s not sound advice. Write some code and put it out for others to read, criticize and castigate you for. Understand that there are some real jerks out there who are absolute geniuses. Don’t be afraid to get some great advice wrapped in some really nasty language. Try to take what’s good about it and leave what’s not. I have a tough time with this myself. I don’t really have any code out there that is available for review (other than my demo code). It takes some guts to do, but in the end, there is no substitute for getting a community of developers to critique your code and give you ways to improve. Get Involved Speaking of community, the local and online user groups and discussion forums are a great place to hear about technologies and techniques you might never come across otherwise. Mostly because you might not know to look. But, once you sit down with a bunch of other developers and start discussing what you’re interested in, you may open up a whole new perspective on it. Don’t just go to the UG meetings and watch the presentations either, get out there and talk, socialize. I realize geeks weren’t meant to necessarily be social creatures, but if you’re amongst other geeks, it’s much easier. I’ve learned more in the last 3-4 years that I have been involved in the community that I did in my previous 8 years of coding without it. Socializing works, even if socialism doesn’t. Continuous Improvement Lean proponents might call this “Kaizen”, but I call it progress. We all know, especially in the technology realm, if you’re not moving ahead, you’re falling behind. It may seem like drinking from a fire hose, but step back and pick out the technologies that speak to you. The ones that may you’re little heart go pitter-patter. Concentrate on those. If you’re still overloaded, pick the best of the best. Just know that if you’re not looking at the code you wrote last week or at least last year with some embarrassment, you’re probably stagnating. That’s about all I can say about that, cause I am all out of clichés to throw at it. :0) Write Code Great painters paint, great writers write, and great developers write code. The most sure-fire way to improve your coding ability is to continue writing code. Don’t just write code that your work throws on you, pick that technology you love or are curious to know more about and walk through some blog demo examples. Take the language you use everyday and try to get it to do something crazy. Who knows, you might create the next Google search algorithm! All in all, being a great developer is about finding yourself in all this code. If it is just a job to you, you will probably never be one of the “Great Developers”, but you’re probably okay with that. If, on the other hand, you do aspire to greatness, get out there and GET it. No one’s going hand it to you.

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  • Blank screen after installing nvidia restricted driver

    - by LaMinifalda
    I have a new machine with a MSI N560GTX Ti Twin Frozr II/OC graphic card and MSI PH67A-C43 (B3) main board. If i install the current nvidia restricted driver and reboot the machine on Natty (64-bit), then i only get a black screen after reboot and my system does not respond. I can´t see the login screen. On nvidia web page i saw that the current driver is 270.41.06. Is that driver used as current driver? Btw, i am an ubuntu/linux beginner and therefore not very familiar with ubuntu. What can i do to solve the black screen problem? EDIT: Setting the nomodeset parameter does not solve the problem. After ubuntu start, first i see the ubuntu logo, then strange pixels and at the end the black screen. HELP! EDIT2: Thank you, but setting the "video=vesa:off gfxpayload=text" parameters do no solve the problem too. Same result as in last edit. HELP. I would like to see Unity. This is my grub: GRUB_DEFAULT=0 GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="video=vesa:off gfxpayload=text nomodeset quiet splash" GRUB_CMDLINE_LINUX=" vga=794" EDIT3: I dont know if it is important. If this edit is unnecessary and helpless I will delete it. There are some log files (Xorg.0.log - Xorg.4.log). I dont know how these log files relate to each other. Please, check the errors listed below. In Xorg.1.log I see the following error: [ 20.603] (EE) Failed to initialize GLX extension (ComIatible NVIDIA X driver not found) In Xorg.2.log I see the following error: [ 25.971] (II) Loading /usr/lib/xorg/modules/libfb.so [ 25.971] (**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32 [ 25.971] (==) NVIDIA(0): RGB weight 888 [ 25.971] (==) NVIDIA(0): Default visual is TrueColor [ 25.971] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0) [ 26.077] (EE) NVIDIA(0): Failed to initialize the NVIDIA GPU at PCI:1:0:0. Please [ 26.078] (EE) NVIDIA(0): check your system's kernel log for additional error [ 26.078] (EE) NVIDIA(0): messages and refer to Chapter 8: Common Problems in the [ 26.078] (EE) NVIDIA(0): README for additional information. [ 26.078] (EE) NVIDIA(0): Failed to initialize the NVIDIA graphics device! [ 26.078] (II) UnloadModule: "nvidia" [ 26.078] (II) Unloading nvidia [ 26.078] (II) UnloadModule: "wfb" [ 26.078] (II) Unloading wfb [ 26.078] (II) UnloadModule: "fb" [ 26.078] (II) Unloading fb [ 26.078] (EE) Screen(s) found, but none have a usable configuration. [ 26.078] Fatal server error: [ 26.078] no screens found [ 26.078] Please consult the The X.Org Found [...] In Xorg.4.log I see the following errors: [ 15.437] (**) NVIDIA(0): Depth 24, (--) framebuffer bpp 32 [ 15.437] (==) NVIDIA(0): RGB weight 888 [ 15.437] (==) NVIDIA(0): Default visual is TrueColor [ 15.437] (==) NVIDIA(0): Using gamma correction (1.0, 1.0, 1.0) [ 15.703] (II) NVIDIA(0): NVIDIA GPU GeForce GTX 560 Ti (GF114) at PCI:1:0:0 (GPU-0) [ 15.703] (--) NVIDIA(0): Memory: 1048576 kBytes [ 15.703] (--) NVIDIA(0): VideoBIOS: 70.24.11.00.00 [ 15.703] (II) NVIDIA(0): Detected PCI Express Link width: 16X [ 15.703] (--) NVIDIA(0): Interlaced video modes are supported on this GPU [ 15.703] (--) NVIDIA(0): Connected display device(s) on GeForce GTX 560 Ti at [ 15.703] (--) NVIDIA(0): PCI:1:0:0 [ 15.703] (--) NVIDIA(0): none [ 15.706] (EE) NVIDIA(0): No display devices found for this X screen. [ 15.943] (II) UnloadModule: "nvidia" [ 15.943] (II) Unloading nvidia [ 15.943] (II) UnloadModule: "wfb" [ 15.943] (II) Unloading wfb [ 15.943] (II) UnloadModule: "fb" [ 15.943] (II) Unloading fb [ 15.943] (EE) Screen(s) found, but none have a usable configuration. [ 15.943] Fatal server error: [ 15.943] no screens found EDIT4 There was a file /etc/X11/xorg.conf. As fossfreedom suggested I executed sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.backup However, there is still the black screen after reboot. EDIT5 Neutro's advice (reinstalling the headers) did not solve the problem, too. :-( Any further help is appreciated! EDIT6 I just installed driver 173.xxx. After reboot the system shows me only "Checking battery state". Just for information. I will google the problem, but help is also appreciated! ;-) EDIT7 When using the free driver (Ubuntu says that the free driver is in use and activated), Xorg.0.log shows the following errors: [ 9.267] (II) LoadModule: "nouveau" [ 9.267] (II) Loading /usr/lib/xorg/modules/drivers/nouveau_drv.so [ 9.267] (II) Module nouveau: vendor="X.Org Foundation" [ 9.267] compiled for 1.10.0, module version = 0.0.16 [ 9.267] Module class: X.Org Video Driver [ 9.267] ABI class: X.Org Video Driver, version 10.0 [ 9.267] (II) LoadModule: "nv" [ 9.267] (WW) Warning, couldn't open module nv [ 9.267] (II) UnloadModule: "nv" [ 9.267] (II) Unloading nv [ 9.267] (EE) Failed to load module "nv" (module does not exist, 0) [ 9.267] (II) LoadModule: "vesa" [...] [ 9.399] drmOpenDevice: node name is /dev/dri/card14 [ 9.402] drmOpenDevice: node name is /dev/dri/card15 [ 9.406] (EE) [drm] failed to open device [ 9.406] (II) Loading /usr/lib/xorg/modules/drivers/vesa_drv.so [ 9.406] (WW) Falling back to old probe method for fbdev [ 9.406] (II) Loading sub module "fbdevhw" [ 9.406] (II) LoadModule: "fbdevhw" EDIT8 In the meanwhile i tried to install WIN7 64 bit on my machine. As a result i got a BSOD after installing the nvidia driver. :-) For this reason i sent my new machine back to the hardware reseller. I will inform you as soon as i have a new system. Thank you all for the great help and support. EDIT9 In the meanwhile I have a complete new system with "only" a MSI N460GTX Hawk, but more RAM. The system works perfect. :-) The original N560GTX had a hardware defect. Is is possible to close this question? THX!

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  • SQL SERVER – Curious Case of Disappearing Rows – ON UPDATE CASCADE and ON DELETE CASCADE – Part 1 of 2

    - by pinaldave
    Social media has created an Always Connected World for us. Recently I enrolled myself to learn new technologies as a student. I had decided to focus on learning and decided not to stay connected on the internet while I am in the learning session. On the second day of the event after the learning was over, I noticed lots of notification from my friend on my various social media handle. He had connected with me on Twitter, Facebook, Google+, LinkedIn, YouTube as well SMS, WhatsApp on the phone, Skype messages and not to forget with a few emails. I right away called him up. The problem was very unique – let us hear the problem in his own words. “Pinal – we are in big trouble we are not able to figure out what is going on. Our product details table is continuously loosing rows. Lots of rows have disappeared since morning and we are unable to find why the rows are getting deleted. We have made sure that there is no DELETE command executed on the table as well. The matter of the fact, we have removed every single place the code which is referencing the table. We have done so many crazy things out of desperation but no luck. The rows are continuously deleted in a random pattern. Do you think we have problems with intrusion or virus?” After describing the problems he had pasted few rants about why I was not available during the day. I think it will be not smart to post those exact words here (due to many reasons). Well, my immediate reaction was to get online with him. His problem was unique to him and his team was all out to fix the issue since morning. As he said he has done quite a lot out in desperation. I started asking questions from audit, policy management and profiling the data. Very soon I realize that I think this problem was not as advanced as it looked. There was no intrusion, SQL Injection or virus issue. Well, long story short first - It was a very simple issue of foreign key created with ON UPDATE CASCADE and ON DELETE CASCADE.  CASCADE allows deletions or updates of key values to cascade through the tables defined to have foreign key relationships that can be traced back to the table on which the modification is performed. ON DELETE CASCADE specifies that if an attempt is made to delete a row with a key referenced by foreign keys in existing rows in other tables, all rows containing those foreign keys are also deleted. ON UPDATE CASCADE specifies that if an attempt is made to update a key value in a row, where the key value is referenced by foreign keys in existing rows in other tables, all of the foreign key values are also updated to the new value specified for the key. (Reference: BOL) In simple words – due to ON DELETE CASCASE whenever is specified when the data from Table A is deleted and if it is referenced in another table using foreign key it will be deleted as well. In my friend’s case, they had two tables, Products and ProductDetails. They had created foreign key referential integrity of the product id between the table. Now the as fall was up they were updating their catalogue. When they were updating the catalogue they were deleting products which are no more available. As the changes were cascading the corresponding rows were also deleted from another table. This is CORRECT. The matter of the fact, there is no error or anything and SQL Server is behaving how it should be behaving. The problem was in the understanding and inappropriate implementations of business logic.  What they needed was Product Master Table, Current Product Catalogue, and Product Order Details History tables. However, they were using only two tables and without proper understanding the relation between them was build using foreign keys. If there were only two table, they should have used soft delete which will not actually delete the record but just hide it from the original product table. This workaround could have got them saved from cascading delete issues. I will be writing a detailed post on the design implications etc in my future post as in above three lines I cannot cover every issue related to designing and it is also not the scope of the blog post. More about designing in future blog posts. Once they learn their mistake, they were happy as there was no intrusion but trust me sometime we are our own enemy and this is a great example of it. In tomorrow’s blog post we will go over their code and workarounds. Feel free to share your opinions, experiences and comments. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • Level of detail algorithm not functioning correctly

    - by Darestium
    I have been working on this problem for months; I have been creating Planet Generator of sorts, after more than 6 months of work I am no closer to finishing it then I was 4 months ago. My problem; The terrain does not subdivide in the correct locations properly, it almost seems as if there is a ghost camera next to me, and the quads subdivide based on the position of this "ghost camera". Here is a video of the broken program: http://www.youtube.com/watch?v=NF_pHeMOju8 The best example of the problem occurs around 0:36. For detail limiting, I am going for a chunked LOD approach, which subdivides the terrain based on how far you are away from it. I use a "depth table" to determine how many subdivisions should take place. void PQuad::construct_depth_table(float distance) { tree[0] = -1; for (int i = 1; i < MAX_DEPTH; i++) { tree[i] = distance; distance /= 2.0f; } } The chuncked LOD relies on the child/parent structure of quads, the depth is determined by a constant e.g: if the constant is 6, there are six levels of detail. The quads which should be drawn go through a distance test from the player to the centre of the quad. void PQuad::get_recursive(glm::vec3 player_pos, std::vector<PQuad*>& out_children) { for (size_t i = 0; i < children.size(); i++) { children[i].get_recursive(player_pos, out_children); } if (this->should_draw(player_pos) || this->depth == 0) { out_children.emplace_back(this); } } bool PQuad::should_draw(glm::vec3 player_position) { float distance = distance3(player_position, centre); if (distance < tree[depth]) { return true; } return false; } The root quad has four children which could be visualized like the following: [] [] [] [] Where each [] is a child. Each child has the same amount of children up until the detail limit, the quads which have are 6 iterations deep are leaf nodes, these nodes have no children. Each node has a corresponding Mesh, each Mesh structure has 16x16 Quad-shapes, each Mesh's Quad-shapes halves in size each detail level deeper - creating more detail. void PQuad::construct_children() { // Calculate the position of the Quad based on the parent's location calculate_position(); if (depth < (int)MAX_DEPTH) { children.reserve((int)NUM_OF_CHILDREN); for (int i = 0; i < (int)NUM_OF_CHILDREN; i++) { children.emplace_back(PQuad(this->face_direction, this->radius)); PQuad *child = &children.back(); child->set_depth(depth + 1); child->set_child_index(i); child->set_parent(this); child->construct_children(); } } else { leaf = true; } } The following function creates the vertices for each quad, I feel that it may play a role in the problem - I just can't determine what is causing the problem. void PQuad::construct_vertices(std::vector<glm::vec3> *vertices, std::vector<Color3> *colors) { vertices->reserve(quad_width * quad_height); for (int y = 0; y < quad_height; y++) { for (int x = 0; x < quad_width; x++) { switch (face_direction) { case YIncreasing: vertices->emplace_back(glm::vec3(position.x + x * element_width, quad_height - 1.0f, -(position.y + y * element_width))); break; case YDecreasing: vertices->emplace_back(glm::vec3(position.x + x * element_width, 0.0f, -(position.y + y * element_width))); break; case XIncreasing: vertices->emplace_back(glm::vec3(quad_width - 1.0f, position.y + y * element_width, -(position.x + x * element_width))); break; case XDecreasing: vertices->emplace_back(glm::vec3(0.0f, position.y + y * element_width, -(position.x + x * element_width))); break; case ZIncreasing: vertices->emplace_back(glm::vec3(position.x + x * element_width, position.y + y * element_width, 0.0f)); break; case ZDecreasing: vertices->emplace_back(glm::vec3(position.x + x * element_width, position.y + y * element_width, -(quad_width - 1.0f))); break; } // Position the bottom, right, front vertex of the cube from being (0,0,0) to (-16, -16, 16) (*vertices)[vertices->size() - 1] -= glm::vec3(quad_width / 2.0f, quad_width / 2.0f, -(quad_width / 2.0f)); colors->emplace_back(Color3(255.0f, 255.0f, 255.0f, false)); } } switch (face_direction) { case YIncreasing: this->centre = glm::vec3(position.x + quad_width / 2.0f, quad_height - 1.0f, -(position.y + quad_height / 2.0f)); break; case YDecreasing: this->centre = glm::vec3(position.x + quad_width / 2.0f, 0.0f, -(position.y + quad_height / 2.0f)); break; case XIncreasing: this->centre = glm::vec3(quad_width - 1.0f, position.y + quad_height / 2.0f, -(position.x + quad_width / 2.0f)); break; case XDecreasing: this->centre = glm::vec3(0.0f, position.y + quad_height / 2.0f, -(position.x + quad_width / 2.0f)); break; case ZIncreasing: this->centre = glm::vec3(position.x + quad_width / 2.0f, position.y + quad_height / 2.0f, 0.0f); break; case ZDecreasing: this->centre = glm::vec3(position.x + quad_width / 2.0f, position.y + quad_height / 2.0f, -(quad_height - 1.0f)); break; } this->centre -= glm::vec3(quad_width / 2.0f, quad_width / 2.0f, -(quad_width / 2.0f)); } Any help in discovering what is causing this "subdivding in the wrong place" would be greatly appreciated.

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  • Common reasons for the &lsquo;Sys is undefined&rsquo; error in ASP.NET Ajax applications

      In this blog I will try to summarize the most common reasons for getting the famous 'Sys is undefined' error when running an Ajax enabled web site or application (there are almost one milion results on Google for that phrase). Where does it come from? In every Ajax web pages source you will see a code like this: <script type="text/javascript"> //<![CDATA[ Sys.WebForms.PageRequestManager._initialize('ScriptManager1', document.getElementById('form1')); Sys.WebForms.PageRequestManager.getInstance()._updateControls([], [], [], 90); //]]> </script>   This is the initialization script of the ScriptManager. So, if for some reason the Sys namespace is not available when the code executes you get the Sys is undefined error. Here are the most common reasons and solutions for that problem:   1. The error occurs when you have added a control from RadControls for ASP.NET AJAX, but your application is not configured to use ASP.NET AJAX. For example, in VS 2005 you created a new Blank Site instead of a new Ajax-Enabled Web Site and the Sys is undefined message pops up. To fix it you need to follow the steps described at Configuring ASP.NET Ajax article (check the topic called Adding ASP.NET AJAX Configuration Elements to an Existing Web Site) or simply create the Ajax-Enabled Web Site. You can also check my other blog post on the matter: Visual Studio 2008: Where is the new ASP.NET Ajax-Enabled Web Site template?   2. Authentication - as the website denies access to all pages to unauthorized users, access to the Telerik.Web.UI.WebResource.axd handler is unauthorized (this is the default handler of RadScriptManager). This causes the handler to serve the content of the login page instead of the combined scripts, hence the error. To solve it - add a <location> section to the application configuration file to allow access to Telerik.Web.UI.WebResource.axd to all users, like: <configuration> ... <location path="Telerik.Web.UI.WebResource.axd"> <system.web> <authorization> <allow users="*"/> </authorization> </system.web> </location> ... </configuration>   Note that the access to the standard ScriptResource.axd and WebResource.axd is automatically allowed for all users (authenticated and unauthenticated), so if you use the ScriptManager instead of RadScriptManager - you will not face this problem. The authentication problem does not manifest when you disable script combining or use the CDN. Adding the above configuration section will make it work with RadScriptManagers combined script.   3. The IE6 browser fails to load the compressed script. The problem does not appear in any other browser. There is a well known bug in the older versions of IE6 which lose the first 2,048 bytes of data that are sent back from a Web server that uses HTTP compression. Latest versions of RadScriptManager does not compress the output at all if the client is IE6, but in the previous versions you need to manually disable the output compression to prevent the error. So, if you get the Sys is undefined error in IE6 - update to the latest version of RadControls or simply disable the output compression.   4. Requests to the *.axd files returns Error Code 404 - Not Found. This could  be fixed easily: Check in the IIS management console that the .axd extension (the default HTTP handler extension) is allowed:     Also check if the Verify if file exists checkbox is unchecked (click on the Edit button appearing in the previous screenshot to check). More information can be found in our troubleshooting article and from the ASP.NET QA team blog post   5. The virtual directory in IIS is not marked as Web Application. Converting it to Web Application should fix the problem.   6. Check for the <xhtmlConformance mode="Legacy"/> option in your web.config and remove it. It would be rather rare to become a victim of this exact case, but still have it in mind. Scott Guthrie describes it in more details   In the above points I mentioned several times the terms web resources, javascript output, compressed script. If you want to find out more about these please see the Web Resources Demystified series of my friend and colleague Atanas Korchev   I hope that one of the above solutions will help you get rid of the Sys is undefined error.   Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • What Counts for A DBA: Observant

    - by drsql
    When walking up to the building where I work, I can see CCTV cameras placed here and there for monitoring access to the building. We are required to wear authorization badges which could be checked at any time. Do we have enemies?  Of course! No one is 100% safe; even if your life is a fairy tale, there is always a witch with an apple waiting to snack you into a thousand years of slumber (or at least so I recollect from elementary school.) Even Little Bo Peep had to keep a wary lookout.    We nerdy types (or maybe it was just me?) generally learned on the school playground to keep an eye open for unprovoked attack from simpler, but more muscular souls, and take steps to avoid messy confrontations well in advance. After we’d apprehensively negotiated adulthood with varying degrees of success, these skills of watching for danger, and avoiding it,  translated quite well to the technical careers so many of us were destined for. And nowhere else is this talent for watching out for irrational malevolence so appropriate as in a career as a production DBA.   It isn’t always active malevolence that the DBA needs to watch out for, but the even scarier quirks of common humanity.  A large number of the issues that occur in the enterprise happen just randomly or even just one time ever in a spurious manner, like in the case where a person decided to download the entire MSDN library of software, cross join every non-indexed billion row table together, and simultaneously stream the HD feed of 5 different sporting events, making the network access slow while the corporate online sales just started. The decent DBA team, like the going, gets tough under such circumstances. They spring into action, checking all of the sources of active information, observes the issue is no longer happening now, figures that either it wasn’t the database’s fault and that the reboot of the whatever device on the network fixed the problem.  This sort of reactive support is good, and will be the initial reaction of even excellent DBAs, but it is not the end of the story if you really want to know what happened and avoid getting called again when it isn’t even your fault.   When fires start raging within the corporate software forest, the DBA’s instinct is to actively find a way to douse the flames and get back to having no one in the company have any idea who they are.  Even better for them is to find a way of killing a potential problem while the fires are small, long before they can be classified as raging. The observant DBA will have already been monitoring the server environment for months in advance.  Most troubles, such as disk space and security intrusions, can be predicted and dealt with by alerting systems, whereas other trouble can come out of the blue and requires a skill of observing ongoing conditions and noticing inexplicable changes that could signal an emerging problem.  You can’t automate the DBA, because the bankable skill of a DBA is in detecting the early signs of unexpected problems, and working out how to deal with them before anyone else notices them.    To achieve this, the DBA will check the situation as it is currently happening,  and in many cases is likely to have been the person who submitted the problem to the level 1 support person in the first place, just to let the support team know of impending issues (always well received, I tell you what!). Database and host computer settings, configurations, and even critical data might be profiled and captured for later comparisons. He’ll use Monitoring tools, built-in, commercial (Not to be too crassly commercial or anything, but there is one such tool is SQL Monitor) and lots of homebrew monitoring tools to monitor for problems and changes in the server environment.   You will know that you have it right when a support call comes in and you can look at your monitoring tools and quickly respond that “response time is well within the normal range, the query that supports the failing interface works perfectly and has actually only been called 67% as often as normal, so I am more than willing to help diagnose the problem, but it isn’t the database server’s fault and is probably a client or networking slowdown causing the interface to be used less frequently than normal.” And that is the best thing for any DBA to observe…

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