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• The 10 Biggest Mistakes in Web Design -- Still!

  After a three-year hiatus, human-computer interaction expert Jakob Nielsen updates his list of the top 10 Web design mistakes you should avoid.

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• The 10 Biggest Mistakes in Web Design -- Still!

  After a three-year hiatus, human-computer interaction expert Jakob Nielsen updates his list of the top 10 Web design mistakes you should avoid.

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• Ada and 'The Book'

  - by Phil Factor

  The long friendship between Charles Babbage and Ada Lovelace created one of the most exciting and mysterious of collaborations ever to have resulted in a technological breakthrough. The fireworks that created by the collision of two prodigious mathematical and creative talents resulted in an invention, the Analytical Engine, which went on to change society fundamentally. However, beyond that, we just don't know what the bulk of their collaborative work was about:;  it was done in strictest secrecy. Even the known outcome of their friendship, the first programmable computer, was shrouded in mystery. At the time, nobody, except close friends and family, had any idea of Ada Byron's contribution to the invention of the ‘Engine’, and how to program it. Her great insight was published in August 1843, under the initials AAL, standing for Ada Augusta Lovelace, her title then being the Countess of Lovelace. It was contained in a lengthy ‘note’ to her translation of a publication that remains the best description of Babbage's amazing Analytical Engine. The secret identity of the person behind those enigmatic initials was finally revealed by Prince de Polignac who, seventy years later, wrote to Ada's daughter to seek confirmation that her mother had, indeed, been the author of the brilliant sentences that described so accurately how Babbage's mechanical computer could be programmed with punch-cards. L.F. Menabrea's paper on the Analytical Engine first appeared in the 'Bibliotheque Universelle de Geneve' in October 1842, and Ada translated it anonymously for Taylor's 'Scientific Memoirs'. Charles Babbage was surprised that she had not written an original paper as she already knew a surprising amount about the way the machine worked. He persuaded her to at least write some explanatory notes. These notes ended up extending to four times the length of the original article and represented the first published account of how a machine could be programmed to perform any calculation. Her example of programming the Bernoulli sequence would have worked on the Analytical engine had the device’s construction been completed, and gave Ada an unassailable claim to have invented the art of programming. What was the reason for Ada's secrecy? She was the only legitimate child of Lord Byron, who was probably the best known celebrity of the age, so she was already famous. She was a senior aristocrat, with titles, a fortune in money and vast estates in the Midlands. She had political influence, and was the cousin of Lord Melbourne, who was the Prime Minister at that time. She was friendly with the young Queen Victoria. Her mathematical activities were a pastime, and not one that would be considered by others to be in keeping with her roles and responsibilities. You wouldn't dare to dream up a fictional heroine like Ada. She was dazzlingly beautiful and talented. She could speak several languages fluently, and play some musical instruments with professional skill. Contemporary accounts refer to her being 'accomplished in science, art and literature'. On top of that, she was a brilliant mathematician, a talent inherited from her mother, Annabella Milbanke. In her mother's circle of literary and scientific friends was Charles Babbage, and Ada's friendship with him dates from her teenage zest for Mathematics. She was one of the first people he'd ever met who understood what he had attempted to achieve with the 'Difference Engine', and with whom he could converse as intellectual equals. He arranged for her to have an education from the most talented academics in the country. Ada melted the heart of the cantankerous genius to the point that he became a faithful and loyal father-figure to her. She was one of the very few who could grasp the principles of the later, and very different, ‘Analytical Engine’ which was designed from the start to tackle a variety of tasks. Sadly, Ada Byron's life ended less than a decade after completing the work that assured her long-term fame, in November 1852. She was dying of cancer, her gambling habits had caused her to run up huge debts, she'd had more than one affairs, and she was being blackmailed. Her brilliant but unempathic mother was nursing her in her final illness, destroying her personal letters and records, and repaying her debts. Her husband was distraught but helpless. Charles Babbage, however, maintained his steadfast paternalistic friendship to the end. She appointed her loyal friend to be her executor. For years, she and Babbage had been working together on a secret project, known only as 'The Book'. We have a clue to what it was in a letter written by her nine years earlier, on 11th August 1843. It was a joint project by herself and Lord Lovelace, her husband, and was intended to involve Babbage's 'undivided energies'. It involved 'consulting your Engine' (it required Babbage’s computer). The letter gives no hint about the project except for the high-minded nature of its purpose, and its highly mathematical nature.  From then on, the surviving correspondence between the two gives only veiled references to 'The Book'. There isn't much, since Babbage later destroyed any letters that could have damaged her reputation within the Establishment. 'I cannot spare the book today, which I am very sorry for. At the moment I want it for constant reference, but I think you can have it tomorrow' (Oct 1844)  And 'I will send you the book directly, and you can say, when you receive it, how long you will want to keep it'. (Nov 1844)  The two of them were obviously intent on the work: She writes, four years later, 'I have an engagement for Wednesday which will prevent me from attending to your wishes about the book' (Dec 1848). This was something that they both needed to work on, but could not do in parallel: 'I will send the book on Tuesday, and it can be left with you till Friday' (11 Feb 1849). After six years work, it had been so well-handled that it was beginning to fall apart: 'Don't forget the new cover you promised for the book. The poor book is very shabby and wants one' (20 Sept 1849). So what was going on? The word 'book' was not a code-word: it was a real book, probably a 'printer's blank', plain paper, but properly bound so printers and publishers could show off how the published work might look. The hints from the correspondence are of advanced mathematics. It is obvious that the book was travelling between them, back and forth, each one working on it for less than a week before passing it back. Ada and her husband were certainly involved in gambling large sums of money on the horses, and so most biographers have concluded that the three of them were trying to calculate the mathematical odds on the horses. This theory has three large problems. Firstly, Ada's original letter proposing the project refers to its high-minded nature. Babbage was temperamentally opposed to gambling and would scarcely have given so much time to the project, even though he was devoted to Ada. Secondly, Babbage would have very soon have realized the hopelessness of trying to beat the bookies. This sort of betting never attracts his type of intellectual background. The third problem is that any work on calculating the odds on horses would not need a well-thumbed book to pass back and forth between them; they would have not had to work in series. The original project was instigated by Ada, along with her husband, William King-Noel, 1st Earl of Lovelace. Charles Babbage was invited to join the project after the couple had come up with the idea. What could William have contributed? One might assume that William was a Bertie Wooster character, addicted only to the joys of the turf, but this was far from the truth. He was a scientist, a Cambridge graduate who was later elected to be a Fellow of the Royal Society. After Eton, he went to Trinity College, Cambridge. On graduation, he entered the diplomatic service and acted as secretary under Lord Nugent, who was Lord Commissioner of the Ionian Islands. William was very friendly with Babbage too, able to discuss scientific matters on equal terms. He was a capable engineer who invented a process for bending large timbers by the application of steam heat. He delivered a paper to the Institution of Civil Engineers in 1849, and received praise from the great engineer, Isambard Kingdom Brunel. As well as being Lord Lieutenant of the County of Surrey for most of Victoria's reign, he had time for a string of scientific and engineering achievements. Whatever the project was, it is unlikely that William was a junior partner. After Ada's death, the project disappeared. Then, two years later, Babbage, through one of his occasional outbursts of temper, demonstrated that he was able to decrypt one of the most powerful of secret codes, Vigenère's autokey cipher.  All contemporary diplomatic and military messages used a variant of this cipher. Babbage had made three important discoveries, namely, the mathematical law of this cipher, the principle of the key periodicity, and the technique of the symmetry of position. The technique is now known as the Kasiski examination, also called the Kasiski test, but Babbage got there first. At one time, he listed amongst his future projects, the writing of a book 'The Philosophy of Decyphering', but it never came to anything. This discovery was going to change the course of history, since it was used to decipher the Russians’ military dispatches in the Crimean war. Babbage himself played a role during the Crimean War as a cryptographical adviser to his friend, Rear-Admiral Sir Francis Beaufort of the Admiralty. This is as much as we can be certain about in trying to make sense of the bulk of the time that Charles Babbage and Ada Lovelace worked together. Nine years of intensive work, involving the 'Engine' and a great deal of mathematics and research seems to have been lost: or has it? I've argued in the past http://www.simple-talk.com/community/blogs/philfactor/archive/2008/06/13/59614.aspx that the cracking of the Vigenère autokey cipher, was a fundamental motive behind the British Government's support and funding of the 'Difference Engine'. The Duke of Wellington, whose understanding of the military significance of being able to read enemy dispatches, was the most steadfast advocate of the project. If the three friends were actually doing the work of cracking codes by mathematical techniques that used the techniques of key periodicity, and symmetry of position (the use of a book being passed quickly to and fro is very suggestive), intending to then use the 'Engine' to do the routine cracking of each dispatch, then this is a rather different story. The project was Ada and William's idea. (William had served in the diplomatic service and would be familiar with the use of codes). This makes Ada Lovelace the initiator of a project which, by giving both Britain, and probably the USA, a diplomatic and military advantage in the second part of the Nineteenth century, changed world history. Ada would never have wanted any credit for cracking the cipher, and developing the method that rendered all contemporary military and diplomatic ciphering techniques nugatory; quite the reverse. And it is clear from the gaps in the record of the letters between the collaborators that the evidence was destroyed, probably on her request by her irascible but intensely honorable executor, Charles Babbage. Charles Babbage toyed with the idea of going public, but the Crimean war put an end to that. The British Government had a valuable secret, and intended to keep it that way. Ada and Charles had quite often discussed possible moneymaking projects that would fund the development of the Analytic Engine, the first programmable computer, but their secret work was never in the running as a potential cash cow. I suspect that the British Government was, even then, working on the concealment of a discovery whose value to the nation depended on it remaining so. The success of code-breaking in the Crimean war, and the American Civil war, led to the British and Americans  subsequently giving much more weight and funding to the science of decryption. Paradoxically, this makes Ada's contribution even closer to the creation of Colossus, the first digital computer, at Bletchley Park, specifically to crack the Nazi’s secret codes.

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• Time Warp

  - by Jesse

  It’s no secret that daylight savings time can wreak havoc on systems that rely heavily on dates. The system I work on is centered around recording dates and times, so naturally my co-workers and I have seen our fair share of date-related bugs. From time to time, however, we come across something that we haven’t seen before. A few weeks ago the following error message started showing up in our logs: “The supplied DateTime represents an invalid time. For example, when the clock is adjusted forward, any time in the period that is skipped is invalid.” This seemed very cryptic, especially since it was coming from areas of our application that are typically only concerned with capturing date-only (no explicit time component) from the user, like reports that take a “start date” and “end date” parameter. For these types of parameters we just leave off the time component when capturing the date values, so midnight is used as a “placeholder” time. How is midnight an “invalid time”? Globalization Is Hard Over the last couple of years our software has been rolled out to users in several countries outside of the United States, including Brazil. Brazil begins and ends daylight savings time at midnight on pre-determined days of the year. On October 16, 2011 at midnight many areas in Brazil began observing daylight savings time at which time their clocks were set forward one hour. This means that at the instant it became midnight on October 16, it actually became 1:00 AM, so any time between 12:00 AM and 12:59:59 AM never actually happened. Because we store all date values in the database in UTC, always adjust any “local” dates provided by a user to UTC before using them as filters in a query. The error we saw was thrown by .NET when trying to convert the Brazilian local time of 2011-10-16 12:00 AM to UTC since that local time never actually existed. We hadn’t experienced this same issue with any of our US customers because the daylight savings time changes in the US occur at 2:00 AM which doesn’t conflict with our “placeholder” time of midnight. Detecting Invalid Times In .NET you might use code similar to the following for converting a local time to UTC: var localDate = new DateTime(2011, 10, 16); //2011-10-16 @ midnight const string timeZoneId = "E. South America Standard Time"; //Windows system timezone Id for "Brasilia" timezone. var localTimeZone = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId); var convertedDate = TimeZoneInfo.ConvertTimeToUtc(localDate, localTimeZone); The code above throws the “invalid time” exception referenced above. We could try to detect whether or not the local time is invalid with something like this: var localDate = new DateTime(2011, 10, 16); //2011-10-16 @ midnight const string timeZoneId = "E. South America Standard Time"; //Windows system timezone Id for "Brasilia" timezone. var localTimeZone = TimeZoneInfo.FindSystemTimeZoneById(timeZoneId); if (localTimeZone.IsInvalidTime(localDate)) localDate = localDate.AddHours(1); var convertedDate = TimeZoneInfo.ConvertTimeToUtc(localDate, localTimeZone); This code works in this particular scenario, but it hardly seems robust. It also does nothing to address the issue that can arise when dealing with the ambiguous times that fall around the end of daylight savings. When we roll the clocks back an hour they record the same hour on the same day twice in a row. To continue on with our Brazil example, on February 19, 2012 at 12:00 AM, it will immediately become February 18, 2012 at 11:00 PM all over again. In this scenario, how should we interpret February 18, 2011 11:30 PM? Enter Noda Time I heard about Noda Time, the .NET port of the Java library Joda Time, a little while back and filed it away in the back of my mind under the “sounds-like-it-might-be-useful-someday” category.  Let’s see how we might deal with the issue of invalid and ambiguous local times using Noda Time (note that as of this writing the samples below will only work using the latest code available from the Noda Time repo on Google Code. The NuGet package version 0.1.0 published 2011-08-19 will incorrectly report unambiguous times as being ambiguous) : var localDateTime = new LocalDateTime(2011, 10, 16, 0, 0); const string timeZoneId = "Brazil/East"; var timezone = DateTimeZone.ForId(timeZoneId); var localDateTimeMaping = timezone.MapLocalDateTime(localDateTime); ZonedDateTime unambiguousLocalDateTime; switch (localDateTimeMaping.Type) { case ZoneLocalMapping.ResultType.Unambiguous: unambiguousLocalDateTime = localDateTimeMaping.UnambiguousMapping; break; case ZoneLocalMapping.ResultType.Ambiguous: unambiguousLocalDateTime = localDateTimeMaping.EarlierMapping; break; case ZoneLocalMapping.ResultType.Skipped: unambiguousLocalDateTime = new ZonedDateTime( localDateTimeMaping.ZoneIntervalAfterTransition.Start, timezone); break; default: throw new InvalidOperationException(string.Format("Unexpected mapping result type: {0}", localDateTimeMaping.Type)); } var convertedDateTime = unambiguousLocalDateTime.ToInstant().ToDateTimeUtc(); Let’s break this sample down: I’m using the Noda Time ‘LocalDateTime’ object to represent the local date and time. I’ve provided the year, month, day, hour, and minute (zeros for the hour and minute here represent midnight). You can think of a ‘LocalDateTime’ as an “invalidated” date and time; there is no information available about the time zone that this date and time belong to, so Noda Time can’t make any guarantees about its ambiguity. The ‘timeZoneId’ in this sample is different than the ones above. In order to use the .NET TimeZoneInfo class we need to provide Windows time zone ids. Noda Time expects an Olson (tz / zoneinfo) time zone identifier and does not currently offer any means of mapping the Windows time zones to their Olson counterparts, though project owner Jon Skeet has said that some sort of mapping will be publicly accessible at some point in the future. I’m making use of the Noda Time ‘DateTimeZone.MapLocalDateTime’ method to disambiguate the original local date time value. This method returns an instance of the Noda Time object ‘ZoneLocalMapping’ containing information about the provided local date time maps to the provided time zone.  The disambiguated local date and time value will be stored in the ‘unambiguousLocalDateTime’ variable as an instance of the Noda Time ‘ZonedDateTime’ object. An instance of this object represents a completely unambiguous point in time and is comprised of a local date and time, a time zone, and an offset from UTC. Instances of ZonedDateTime can only be created from within the Noda Time assembly (the constructor is ‘internal’) to ensure to callers that each instance represents an unambiguous point in time. The value of the ‘unambiguousLocalDateTime’ might vary depending upon the ‘ResultType’ returned by the ‘MapLocalDateTime’ method. There are three possible outcomes: If the provided local date time is unambiguous in the provided time zone I can immediately set the ‘unambiguousLocalDateTime’ variable from the ‘Unambiguous Mapping’ property of the mapping returned by the ‘MapLocalDateTime’ method. If the provided local date time is ambiguous in the provided time zone (i.e. it falls in an hour that was repeated when moving clocks backward from Daylight Savings to Standard Time), I can use the ‘EarlierMapping’ property to get the earlier of the two possible local dates to define the unambiguous local date and time that I need. I could have also opted to use the ‘LaterMapping’ property in this case, or even returned an error and asked the user to specify the proper choice. The important thing to note here is that as the programmer I’ve been forced to deal with what appears to be an ambiguous date and time. If the provided local date time represents a skipped time (i.e. it falls in an hour that was skipped when moving clocks forward from Standard Time to Daylight Savings Time),  I have access to the time intervals that fell immediately before and immediately after the point in time that caused my date to be skipped. In this case I have opted to disambiguate my local date and time by moving it forward to the beginning of the interval immediately following the skipped period. Again, I could opt to use the end of the interval immediately preceding the skipped period, or raise an error depending on the needs of the application. The point of this code is to convert a local date and time to a UTC date and time for use in a SQL Server database, so the final ‘convertedDate’  variable (typed as a plain old .NET DateTime) has its value set from a Noda Time ‘Instant’. An 'Instant’ represents a number of ticks since 1970-01-01 at midnight (Unix epoch) and can easily be converted to a .NET DateTime in the UTC time zone using the ‘ToDateTimeUtc()’ method. This sample is admittedly contrived and could certainly use some refactoring, but I think it captures the general approach needed to take a local date and time and convert it to UTC with Noda Time. At first glance it might seem that Noda Time makes this “simple” code more complicated and verbose because it forces you to explicitly deal with the local date disambiguation, but I feel that the length and complexity of the Noda Time sample is proportionate to the complexity of the problem. Using TimeZoneInfo leaves you susceptible to overlooking ambiguous and skipped times that could result in run-time errors or (even worse) run-time data corruption in the form of a local date and time being adjusted to UTC incorrectly. I should point out that this research is my first look at Noda Time and I know that I’ve only scratched the surface of its full capabilities. I also think it’s safe to say that it’s still beta software for the time being so I’m not rushing out to use it production systems just yet, but I will definitely be tinkering with it more and keeping an eye on it as it progresses.

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• Ancillary Objects: Separate Debug ELF Files For Solaris

  - by Ali Bahrami

  We introduced a new object ELF object type in Solaris 11 Update 1 called the Ancillary Object. This posting describes them, using material originally written during their development, the PSARC arc case, and the Solaris Linker and Libraries Manual. ELF objects contain allocable sections, which are mapped into memory at runtime, and non-allocable sections, which are present in the file for use by debuggers and observability tools, but which are not mapped or used at runtime. Typically, all of these sections exist within a single object file. Ancillary objects allow them to instead go into a separate file. There are different reasons given for wanting such a feature. One can debate whether the added complexity is worth the benefit, and in most cases it is not. However, one important case stands out — customers with very large 32-bit objects who are not ready or able to make the transition to 64-bits. We have customers who build extremely large 32-bit objects. Historically, the debug sections in these objects have used the stabs format, which is limited, but relatively compact. In recent years, the industry has transitioned to the powerful but verbose DWARF standard. In some cases, the size of these debug sections is large enough to push the total object file size past the fundamental 4GB limit for 32-bit ELF object files. The best, and ultimately only, solution to overly large objects is to transition to 64-bits. However, consider environments where: Hundreds of users may be executing the code on large shared systems. (32-bits use less memory and bus bandwidth, and on sparc runs just as fast as 64-bit code otherwise). Complex finely tuned code, where the original authors may no longer be available. Critical production code, that was expensive to qualify and bring online, and which is otherwise serving its intended purpose without issue. Users in these risk adverse and/or high scale categories have good reasons to push 32-bits objects to the limit before moving on. Ancillary objects offer these users a longer runway. Design The design of ancillary objects is intended to be simple, both to help human understanding when examining elfdump output, and to lower the bar for debuggers such as dbx to support them. The primary and ancillary objects have the same set of section headers, with the same names, in the same order (i.e. each section has the same index in both files). A single added section of type SHT_SUNW_ANCILLARY is added to both objects, containing information that allows a debugger to identify and validate both files relative to each other. Given one of these files, the ancillary section allows you to identify the other. Allocable sections go in the primary object, and non-allocable ones go into the ancillary object. A small set of non-allocable objects, notably the symbol table, are copied into both objects. As noted above, most sections are only written to one of the two objects, but both objects have the same section header array. The section header in the file that does not contain the section data is tagged with the SHF_SUNW_ABSENT section header flag to indicate its placeholder status. Compiler writers and others who produce objects can set the SUNW_SHF_PRIMARY section header flag to mark non-allocable sections that should go to the primary object rather than the ancillary. If you don't request an ancillary object, the Solaris ELF format is unchanged. Users who don't use ancillary objects do not pay for the feature. This is important, because they exist to serve a small subset of our users, and must not complicate the common case. If you do request an ancillary object, the runtime behavior of the primary object will be the same as that of a normal object. There is no added runtime cost. The primary and ancillary object together represent a logical single object. This is facilitated by the use of a single set of section headers. One can easily imagine a tool that can merge a primary and ancillary object into a single file, or the reverse. (Note that although this is an interesting intellectual exercise, we don't actually supply such a tool because there's little practical benefit above and beyond using ld to create the files). Among the benefits of this approach are: There is no need for per-file symbol tables to reflect the contents of each file. The same symbol table that would be produced for a standard object can be used. The section contents are identical in either case — there is no need to alter data to accommodate multiple files. It is very easy for a debugger to adapt to these new files, and the processing involved can be encapsulated in input/output routines. Most of the existing debugger implementation applies without modification. The limit of a 4GB 32-bit output object is now raised to 4GB of code, and 4GB of debug data. There is also the future possibility (not currently supported) to support multiple ancillary objects, each of which could contain up to 4GB of additional debug data. It must be noted however that the 32-bit DWARF debug format is itself inherently 32-bit limited, as it uses 32-bit offsets between debug sections, so the ability to employ multiple ancillary object files may not turn out to be useful. Using Ancillary Objects (From the Solaris Linker and Libraries Guide) By default, objects contain both allocable and non-allocable sections. Allocable sections are the sections that contain executable code and the data needed by that code at runtime. Non-allocable sections contain supplemental information that is not required to execute an object at runtime. These sections support the operation of debuggers and other observability tools. The non-allocable sections in an object are not loaded into memory at runtime by the operating system, and so, they have no impact on memory use or other aspects of runtime performance no matter their size. For convenience, both allocable and non-allocable sections are normally maintained in the same file. However, there are situations in which it can be useful to separate these sections. To reduce the size of objects in order to improve the speed at which they can be copied across wide area networks. To support fine grained debugging of highly optimized code requires considerable debug data. In modern systems, the debugging data can easily be larger than the code it describes. The size of a 32-bit object is limited to 4 Gbytes. In very large 32-bit objects, the debug data can cause this limit to be exceeded and prevent the creation of the object. To limit the exposure of internal implementation details. Traditionally, objects have been stripped of non-allocable sections in order to address these issues. Stripping is effective, but destroys data that might be needed later. The Solaris link-editor can instead write non-allocable sections to an ancillary object. This feature is enabled with the -z ancillary command line option. $ ld ... -z ancillary[=outfile] ...By default, the ancillary file is given the same name as the primary output object, with a .anc file extension. However, a different name can be provided by providing an outfile value to the -z ancillary option. When -z ancillary is specified, the link-editor performs the following actions. All allocable sections are written to the primary object. In addition, all non-allocable sections containing one or more input sections that have the SHF_SUNW_PRIMARY section header flag set are written to the primary object. All remaining non-allocable sections are written to the ancillary object. The following non-allocable sections are written to both the primary object and ancillary object. .shstrtab The section name string table. .symtab The full non-dynamic symbol table. .symtab_shndx The symbol table extended index section associated with .symtab. .strtab The non-dynamic string table associated with .symtab. .SUNW_ancillary Contains the information required to identify the primary and ancillary objects, and to identify the object being examined. The primary object and all ancillary objects contain the same array of sections headers. Each section has the same section index in every file. Although the primary and ancillary objects all define the same section headers, the data for most sections will be written to a single file as described above. If the data for a section is not present in a given file, the SHF_SUNW_ABSENT section header flag is set, and the sh_size field is 0. This organization makes it possible to acquire a full list of section headers, a complete symbol table, and a complete list of the primary and ancillary objects from either of the primary or ancillary objects. The following example illustrates the underlying implementation of ancillary objects. An ancillary object is created by adding the -z ancillary command line option to an otherwise normal compilation. The file utility shows that the result is an executable named a.out, and an associated ancillary object named a.out.anc. $ cat hello.c #include <stdio.h> int main(int argc, char **argv) { (void) printf("hello, world\n"); return (0); } $ cc -g -zancillary hello.c $ file a.out a.out.anc a.out: ELF 32-bit LSB executable 80386 Version 1 [FPU], dynamically linked, not stripped, ancillary object a.out.anc a.out.anc: ELF 32-bit LSB ancillary 80386 Version 1, primary object a.out $ ./a.out hello worldThe resulting primary object is an ordinary executable that can be executed in the usual manner. It is no different at runtime than an executable built without the use of ancillary objects, and then stripped of non-allocable content using the strip or mcs commands. As previously described, the primary object and ancillary objects contain the same section headers. To see how this works, it is helpful to use the elfdump utility to display these section headers and compare them. The following table shows the section header information for a selection of headers from the previous link-edit example. Index Section Name Type Primary Flags Ancillary Flags Primary Size Ancillary Size 13 .text PROGBITS ALLOC EXECINSTR ALLOC EXECINSTR SUNW_ABSENT 0x131 0 20 .data PROGBITS WRITE ALLOC WRITE ALLOC SUNW_ABSENT 0x4c 0 21 .symtab SYMTAB 0 0 0x450 0x450 22 .strtab STRTAB STRINGS STRINGS 0x1ad 0x1ad 24 .debug_info PROGBITS SUNW_ABSENT 0 0 0x1a7 28 .shstrtab STRTAB STRINGS STRINGS 0x118 0x118 29 .SUNW_ancillary SUNW_ancillary 0 0 0x30 0x30 The data for most sections is only present in one of the two files, and absent from the other file. The SHF_SUNW_ABSENT section header flag is set when the data is absent. The data for allocable sections needed at runtime are found in the primary object. The data for non-allocable sections used for debugging but not needed at runtime are placed in the ancillary file. A small set of non-allocable sections are fully present in both files. These are the .SUNW_ancillary section used to relate the primary and ancillary objects together, the section name string table .shstrtab, as well as the symbol table.symtab, and its associated string table .strtab. It is possible to strip the symbol table from the primary object. A debugger that encounters an object without a symbol table can use the .SUNW_ancillary section to locate the ancillary object, and access the symbol contained within. The primary object, and all associated ancillary objects, contain a .SUNW_ancillary section that allows all the objects to be identified and related together. $ elfdump -T SUNW_ancillary a.out a.out.anc a.out: Ancillary Section: .SUNW_ancillary index tag value [0] ANC_SUNW_CHECKSUM 0x8724 [1] ANC_SUNW_MEMBER 0x1 a.out [2] ANC_SUNW_CHECKSUM 0x8724 [3] ANC_SUNW_MEMBER 0x1a3 a.out.anc [4] ANC_SUNW_CHECKSUM 0xfbe2 [5] ANC_SUNW_NULL 0 a.out.anc: Ancillary Section: .SUNW_ancillary index tag value [0] ANC_SUNW_CHECKSUM 0xfbe2 [1] ANC_SUNW_MEMBER 0x1 a.out [2] ANC_SUNW_CHECKSUM 0x8724 [3] ANC_SUNW_MEMBER 0x1a3 a.out.anc [4] ANC_SUNW_CHECKSUM 0xfbe2 [5] ANC_SUNW_NULL 0 The ancillary sections for both objects contain the same number of elements, and are identical except for the first element. Each object, starting with the primary object, is introduced with a MEMBER element that gives the file name, followed by a CHECKSUM that identifies the object. In this example, the primary object is a.out, and has a checksum of 0x8724. The ancillary object is a.out.anc, and has a checksum of 0xfbe2. The first element in a .SUNW_ancillary section, preceding the MEMBER element for the primary object, is always a CHECKSUM element, containing the checksum for the file being examined. The presence of a .SUNW_ancillary section in an object indicates that the object has associated ancillary objects. The names of the primary and all associated ancillary objects can be obtained from the ancillary section from any one of the files. It is possible to determine which file is being examined from the larger set of files by comparing the first checksum value to the checksum of each member that follows. Debugger Access and Use of Ancillary Objects Debuggers and other observability tools must merge the information found in the primary and ancillary object files in order to build a complete view of the object. This is equivalent to processing the information from a single file. This merging is simplified by the primary object and ancillary objects containing the same section headers, and a single symbol table. The following steps can be used by a debugger to assemble the information contained in these files. Starting with the primary object, or any of the ancillary objects, locate the .SUNW_ancillary section. The presence of this section identifies the object as part of an ancillary group, contains information that can be used to obtain a complete list of the files and determine which of those files is the one currently being examined. Create a section header array in memory, using the section header array from the object being examined as an initial template. Open and read each file identified by the .SUNW_ancillary section in turn. For each file, fill in the in-memory section header array with the information for each section that does not have the SHF_SUNW_ABSENT flag set. The result will be a complete in-memory copy of the section headers with pointers to the data for all sections. Once this information has been acquired, the debugger can proceed as it would in the single file case, to access and control the running program. Note - The ELF definition of ancillary objects provides for a single primary object, and an arbitrary number of ancillary objects. At this time, the Oracle Solaris link-editor only produces a single ancillary object containing all non-allocable sections. This may change in the future. Debuggers and other observability tools should be written to handle the general case of multiple ancillary objects. ELF Implementation Details (From the Solaris Linker and Libraries Guide) To implement ancillary objects, it was necessary to extend the ELF format to add a new object type (ET_SUNW_ANCILLARY), a new section type (SHT_SUNW_ANCILLARY), and 2 new section header flags (SHF_SUNW_ABSENT, SHF_SUNW_PRIMARY). In this section, I will detail these changes, in the form of diffs to the Solaris Linker and Libraries manual. Part IV ELF Application Binary Interface Chapter 13: Object File Format Object File Format Edit Note: This existing section at the beginning of the chapter describes the ELF header. There's a table of object file types, which now includes the new ET_SUNW_ANCILLARY type. e_type Identifies the object file type, as listed in the following table. NameValueMeaning ET_NONE0No file type ET_REL1Relocatable file ET_EXEC2Executable file ET_DYN3Shared object file ET_CORE4Core file ET_LOSUNW0xfefeStart operating system specific range ET_SUNW_ANCILLARY0xfefeAncillary object file ET_HISUNW0xfefdEnd operating system specific range ET_LOPROC0xff00Start processor-specific range ET_HIPROC0xffffEnd processor-specific range Sections Edit Note: This overview section defines the section header structure, and provides a high level description of known sections. It was updated to define the new SHF_SUNW_ABSENT and SHF_SUNW_PRIMARY flags and the new SHT_SUNW_ANCILLARY section. ... sh_type Categorizes the section's contents and semantics. Section types and their descriptions are listed in Table 13-5. sh_flags Sections support 1-bit flags that describe miscellaneous attributes. Flag definitions are listed in Table 13-8. ... Table 13-5 ELF Section Types, sh_type NameValue . . . SHT_LOSUNW0x6fffffee SHT_SUNW_ancillary0x6fffffee . . . ... SHT_LOSUNW - SHT_HISUNW Values in this inclusive range are reserved for Oracle Solaris OS semantics. SHT_SUNW_ANCILLARY Present when a given object is part of a group of ancillary objects. Contains information required to identify all the files that make up the group. See Ancillary Section. ... Table 13-8 ELF Section Attribute Flags NameValue . . . SHF_MASKOS0x0ff00000 SHF_SUNW_NODISCARD0x00100000 SHF_SUNW_ABSENT0x00200000 SHF_SUNW_PRIMARY0x00400000 SHF_MASKPROC0xf0000000 . . . ... SHF_SUNW_ABSENT Indicates that the data for this section is not present in this file. When ancillary objects are created, the primary object and any ancillary objects, will all have the same section header array, to facilitate merging them to form a complete view of the object, and to allow them to use the same symbol tables. Each file contains a subset of the section data. The data for allocable sections is written to the primary object while the data for non-allocable sections is written to an ancillary file. The SHF_SUNW_ABSENT flag is used to indicate that the data for the section is not present in the object being examined. When the SHF_SUNW_ABSENT flag is set, the sh_size field of the section header must be 0. An application encountering an SHF_SUNW_ABSENT section can choose to ignore the section, or to search for the section data within one of the related ancillary files. SHF_SUNW_PRIMARY The default behavior when ancillary objects are created is to write all allocable sections to the primary object and all non-allocable sections to the ancillary objects. The SHF_SUNW_PRIMARY flag overrides this behavior. Any output section containing one more input section with the SHF_SUNW_PRIMARY flag set is written to the primary object without regard for its allocable status. ... Two members in the section header, sh_link, and sh_info, hold special information, depending on section type. Table 13-9 ELF sh_link and sh_info Interpretation sh_typesh_linksh_info . . . SHT_SUNW_ANCILLARY The section header index of the associated string table. 0 . . . Special Sections Edit Note: This section describes the sections used in Solaris ELF objects, using the types defined in the previous description of section types. It was updated to define the new .SUNW_ancillary (SHT_SUNW_ANCILLARY) section. Various sections hold program and control information. Sections in the following table are used by the system and have the indicated types and attributes. Table 13-10 ELF Special Sections NameTypeAttribute . . . .SUNW_ancillarySHT_SUNW_ancillaryNone . . . ... .SUNW_ancillary Present when a given object is part of a group of ancillary objects. Contains information required to identify all the files that make up the group. See Ancillary Section for details. ... Ancillary Section Edit Note: This new section provides the format reference describing the layout of a .SUNW_ancillary section and the meaning of the various tags. Note that these sections use the same tag/value concept used for dynamic and capabilities sections, and will be familiar to anyone used to working with ELF. In addition to the primary output object, the Solaris link-editor can produce one or more ancillary objects. Ancillary objects contain non-allocable sections that would normally be written to the primary object. When ancillary objects are produced, the primary object and all of the associated ancillary objects contain a SHT_SUNW_ancillary section, containing information that identifies these related objects. Given any one object from such a group, the ancillary section provides the information needed to identify and interpret the others. This section contains an array of the following structures. See sys/elf.h. typedef struct { Elf32_Word a_tag; union { Elf32_Word a_val; Elf32_Addr a_ptr; } a_un; } Elf32_Ancillary; typedef struct { Elf64_Xword a_tag; union { Elf64_Xword a_val; Elf64_Addr a_ptr; } a_un; } Elf64_Ancillary; For each object with this type, a_tag controls the interpretation of a_un. a_val These objects represent integer values with various interpretations. a_ptr These objects represent file offsets or addresses. The following ancillary tags exist. Table 13-NEW1 ELF Ancillary Array Tags NameValuea_un ANC_SUNW_NULL0Ignored ANC_SUNW_CHECKSUM1a_val ANC_SUNW_MEMBER2a_ptr ANC_SUNW_NULL Marks the end of the ancillary section. ANC_SUNW_CHECKSUM Provides the checksum for a file in the c_val element. When ANC_SUNW_CHECKSUM precedes the first instance of ANC_SUNW_MEMBER, it provides the checksum for the object from which the ancillary section is being read. When it follows an ANC_SUNW_MEMBER tag, it provides the checksum for that member. ANC_SUNW_MEMBER Specifies an object name. The a_ptr element contains the string table offset of a null-terminated string, that provides the file name. An ancillary section must always contain an ANC_SUNW_CHECKSUM before the first instance of ANC_SUNW_MEMBER, identifying the current object. Following that, there should be an ANC_SUNW_MEMBER for each object that makes up the complete set of objects. Each ANC_SUNW_MEMBER should be followed by an ANC_SUNW_CHECKSUM for that object. A typical ancillary section will therefore be structured as: TagMeaning ANC_SUNW_CHECKSUMChecksum of this object ANC_SUNW_MEMBERName of object #1 ANC_SUNW_CHECKSUMChecksum for object #1 . . . ANC_SUNW_MEMBERName of object N ANC_SUNW_CHECKSUMChecksum for object N ANC_SUNW_NULL An object can therefore identify itself by comparing the initial ANC_SUNW_CHECKSUM to each of the ones that follow, until it finds a match. Related Other Work The GNU developers have also encountered the need/desire to support separate debug information files, and use the solution detailed at http://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html. At the current time, the separate debug file is constructed by building the standard object first, and then copying the debug data out of it in a separate post processing step, Hence, it is limited to a total of 4GB of code and debug data, just as a single object file would be. They are aware of this, and I have seen online comments indicating that they may add direct support for generating these separate files to their link-editor. It is worth noting that the GNU objcopy utility is available on Solaris, and that the Studio dbx debugger is able to use these GNU style separate debug files even on Solaris. Although this is interesting in terms giving Linux users a familiar environment on Solaris, the 4GB limit means it is not an answer to the problem of very large 32-bit objects. We have also encountered issues with objcopy not understanding Solaris-specific ELF sections, when using this approach. The GNU community also has a current effort to adapt their DWARF debug sections in order to move them to separate files before passing the relocatable objects to the linker. The details of Project Fission can be found at http://gcc.gnu.org/wiki/DebugFission. The goal of this project appears to be to reduce the amount of data seen by the link-editor. The primary effort revolves around moving DWARF data to separate .dwo files so that the link-editor never encounters them. The details of modifying the DWARF data to be usable in this form are involved — please see the above URL for details.

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• Virtual Box - How to open a .VDI Virtual Machine

  - by [email protected]

   How to open a .VDI Virtual MachineSometimes someone share with us one Virtual machine with extension .VDI, after that we can wonder how and what with?Well the answer is... It is a VirtualBox - Virtual Machine. If you have not downloaded it you can do this easily just follow this post.http://listeningoracle.blogspot.com/2010/04/que-es-virtualbox.htmlor http://oracleoforacle.wordpress.com/2010/04/14/ques-es-virtualbox/Ok, Now with VirtualBox Installed open it and proceed with the following:1. Open the Virtual File Manager. 2. Click on Actions ? Add and select the .VDI file Click "Ok"3. Now we can register the new Virtual Machine - Click New, and Click Next4. Write down a Name for the virtual Machine a proceed to select a Operating System and Version. (In this case it is a Linux (Oracle Enterprise Linux or RedHat)Click Next5. Select the memory amount base for the Virtual Machine (Minimal 1280 for our case) - Click Next6. Select the Disk 11GR2_OEL5_32GB.vdi it was added in the virtual media manager in the step 2. Dont forget let selected Boot hard Disk (Primary Master) . Given it is the only disk assigned to the virtual machine.Click Next7. Click Finish8. This step is important. Once you have click on the settings Button.9. On General option click the advanced settings. Here you must change the default directory to save your Snapshots; my recommendation set it to the same directory where the .Vdi file is. Otherwise you can have the same Virtual Machine and its snapshots in different paths.10. Now Click on System, and proceed to assign the correct memory (If you did not before) Note: Enable "Enable IO APIC" if you are planning to assign more than one CPU to the Virtual Machine.Define the processors for the Virtual machine. If you processor is dual core choose 211. Select the video memory amount you want to assign to the Virtual Machine 12. Associated more storage disk to the Virtual machine, if you have more VDI files. (Not our case)The disk must be selected as IDE Primary Master. 13. Well you can verify the other options, but with these changes you will be able to start the VM.Note: Sometime the VM owner may share some instructions, if so follow his instructions.14. Finally Start the Virtual Machine (Click > Start)

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• MacGyver Moments

  - by KKline

  In case you haven't heard, your MacGyver Moments are those times when you improvised an excellent solution to a problem using non-traditional materials, techniques, or tools......(read more)

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• SQL SERVER – Challenge – Puzzle – Usage of FAST Hint

  - by pinaldave

  I was recently working with various SQL Server Hints. After working for a day on various hints, I realize that for one hint, I am not able to come up with good example. The hint is FAST. Let us look at the definition of the FAST hint from the Book On-Line. FAST number_rows Specifies that the query is optimized for fast retrieval of the first number_rows. This is a nonnegative integer. After the first number_rows are returned, the query continues execution and produces its full result set. Now the question is in what condition this hint can be useful. I have tried so many different combination, I have found this hint does not make much performance difference, infect I did not notice any change in time taken to load the resultset. I noticed that this hint does not change number of the page read to return result. Now when there is difference in performance is expected because if you read the what FAST hint does is that it only returns first few results FAST – which does not mean there will be difference in performance. I also understand that this hint gives the guidance/suggestions/hint to query optimizer that there are only 100 rows are in expected resultset. This tricking the optimizer to think there are only 100 rows and which (may) lead to render different execution plan than the one which it would have taken in normal case (without hint). Again, not necessarily, this will happen always. Now if you read above discussion, you will find that basic understanding of the hint is very clear to me but I still feel that I am missing something. Here are my questions: 1) In what condition this hint can be useful? What is the case, when someone want to see first few rows early because my experience suggests that when first few rows are rendered remaining rows are rendered as well. 2) Is there any way application can retrieve the fast fetched rows from SQL Server? 3) Do you use this hint in your application? Why? When? and How? Here are few examples I have attempted during the my experiment and found there is no difference in execution plan except its estimated number of rows are different leading optimizer think that the cost is less but in reality that is not the case. USE AdventureWorks GO SET STATISTICS IO ON SET STATISTICS TIME ON GO --------------------------------------------- -- Table Scan with Fast Hint SELECT * FROM Sales.SalesOrderDetail GO SELECT * FROM Sales.SalesOrderDetail OPTION (FAST 100) GO --------------------------------------------- -- Table Scan with Where on Index Key SELECT * FROM Sales.SalesOrderDetail WHERE OrderQty = 14 GO SELECT * FROM Sales.SalesOrderDetail WHERE OrderQty = 14 OPTION (FAST 100) GO --------------------------------------------- -- Table Scan with Where on Index Key SELECT * FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID < 1000 GO SELECT * FROM Sales.SalesOrderDetail WHERE SalesOrderDetailID < 1000 OPTION (FAST 100) GO Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Pinal Dave, SQL, SQL Authority, SQL Puzzle, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• SQL SERVER – Solution – Puzzle – Statistics are not Updated but are Created Once

  - by pinaldave

  Earlier I asked puzzle why statistics are not updated. Read the complete details over here: Statistics are not Updated but are Created Once In the question I have demonstrated even though statistics should have been updated after lots of insert in the table are not updated.(Read the details SQL SERVER – When are Statistics Updated – What triggers Statistics to Update) In this example I have created following situation: Create Table Insert 1000 Records Check the Statistics Now insert 10 times more 10,000 indexes Check the Statistics – it will be NOT updated Auto Update Statistics and Auto Create Statistics for database is TRUE Now I have requested two things in the example 1) Why this is happening? 2) How to fix this issue? I have many answers – here is the how I fixed it which has resolved the issue for me. NOTE: There are multiple answers to this problem and I will do my best to list all. Solution: Create nonclustered Index on column City Here is the working example for the same. Let us understand this script and there is added explanation at the end. -- Execution Plans Difference -- Estimated Execution Plan Vs Actual Execution Plan -- Create Sample Database CREATE DATABASE SampleDB GO USE SampleDB GO -- Create Table CREATE TABLE ExecTable (ID INT, FirstName VARCHAR(100), LastName VARCHAR(100), City VARCHAR(100)) GO CREATE NONCLUSTERED INDEX IX_ExecTable1 ON ExecTable (City); GO -- Insert One Thousand Records -- INSERT 1 INSERT INTO ExecTable (ID,FirstName,LastName,City) SELECT TOP 1000 ROW_NUMBER() OVER (ORDER BY a.name) RowID, 'Bob', CASE WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%2 = 1 THEN 'Smith' ELSE 'Brown' END, CASE WHEN ROW_NUMBER() OVER (ORDER BY a.name)%20 = 1 THEN 'New York' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 5 THEN 'San Marino' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 3 THEN 'Los Angeles' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 7 THEN 'La Cinega' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 13 THEN 'San Diego' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 17 THEN 'Las Vegas' ELSE 'Houston' END FROM sys.all_objects a CROSS JOIN sys.all_objects b GO -- Display statistics of the table sp_helpstats N'ExecTable', 'ALL' GO -- Select Statement SELECT FirstName, LastName, City FROM ExecTable WHERE City  = 'New York' GO -- Display statistics of the table sp_helpstats N'ExecTable', 'ALL' GO -- Replace your Statistics over here DBCC SHOW_STATISTICS('ExecTable', IX_ExecTable1); GO -------------------------------------------------------------- -- Round 2 -- Insert One Thousand Records -- INSERT 2 INSERT INTO ExecTable (ID,FirstName,LastName,City) SELECT TOP 1000 ROW_NUMBER() OVER (ORDER BY a.name) RowID, 'Bob', CASE WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%2 = 1 THEN 'Smith' ELSE 'Brown' END, CASE WHEN ROW_NUMBER() OVER (ORDER BY a.name)%20 = 1 THEN 'New York' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 5 THEN 'San Marino' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 3 THEN 'Los Angeles' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 7 THEN 'La Cinega' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 13 THEN 'San Diego' WHEN  ROW_NUMBER() OVER (ORDER BY a.name)%20 = 17 THEN 'Las Vegas' ELSE 'Houston' END FROM sys.all_objects a CROSS JOIN sys.all_objects b GO -- Select Statement SELECT FirstName, LastName, City FROM ExecTable WHERE City  = 'New York' GO -- Display statistics of the table sp_helpstats N'ExecTable', 'ALL' GO -- Replace your Statistics over here DBCC SHOW_STATISTICS('ExecTable', IX_ExecTable1); GO -- Clean up Database DROP TABLE ExecTable GO When I created non clustered index on the column city, it also created statistics on the same column with same name as index. When we populate the data in the column the index is update – resulting execution plan to be invalided – this leads to the statistics to be updated in next execution of SELECT. This behavior does not happen on Heap or column where index is auto created. If you explicitly update the index, often you can see the statistics are updated as well. You can see this is for sure happening if you follow the tell of John Sansom. John Sansom‘s suggestion: That was fun! Although the column statistics are invalidated by the time the second select statement is executed, the query is not compiled/recompiled but instead the existing query plan is reused. It is the “next” compiled query against the column statistics that will see that they are out of date and will then in turn instantiate the action of updating statistics. You can see this in action by forcing the second statement to recompile. SELECT FirstName, LastName, City FROM ExecTable WHERE City = ‘New York’ option(RECOMPILE) GO Kevin Cross also have another suggestion: I agree with John. It is reusing the Execution Plan. Aside from OPTION(RECOMPILE), clearing the Execution Plan Cache before the subsequent tests will also work. i.e., run this before round 2: ————————————————————– – Clear execution plan cache before next test DBCC FREEPROCCACHE WITH NO_INFOMSGS; ————————————————————– Nice puzzle! Kevin As this was puzzle John and Kevin both got the correct answer, there was no condition for answer to be part of best practices. I know John and he is finest DBA around – his tremendous knowledge has always impressed me. John and Kevin both will agree that clearing cache either using DBCC FREEPROCCACHE and recompiling each query every time is for sure not good advice on production server. It is correct answer but not best practice. By the way, if you have better solution or have better suggestion please advise. I am open to change my answer and publish further improvement to this solution. On very separate note, I like to have clustered index on my Primary Key, which I have not mentioned here as it is out of the scope of this puzzle. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, Readers Contribution, Readers Question, SQL, SQL Authority, SQL Index, SQL Puzzle, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Statistics

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• Ask the Readers: Do You Prefer Computers, Game Consoles, or Other Devices for Your Gaming Needs?

  - by Asian Angel

  Nearly everyone who has access to a computer will play games on it at some point, but many people also use a separate game platform as well. What we would like to know this week is if you prefer using a computer, game consoles, or other devices for your gaming needs. Photo of Faith and Kate Connors from Mirror’s Edge by Tamahikari Tammas. Video games are a perfect way to relax and have fun at home (or at work if you can sneak in some game time!). The increasing variety of devices available with each passing year are making it easier to have access to a gaming platform to suit your needs or “darkest gaming desires”. For many people their computers are the perfect platform…they can play Flash-based games in their browsers, use the default set of games that come with their system, and install any extras that catch their eyes. The added benefit is that when game time is over they can drop right into their browsing, e-mail, personal projects, or work without having to switch hardware. The convenience of the “all-in-one” platform is certainly appealing! Perhaps you prefer to use your computer for other activities outside of gaming and own one or more separate game consoles. You might have chosen an Xbox, Playstation, or Nintendo for example. Maybe a hand-held is preferable for its’ size and portability. Then there are mobile phones and the iPad… With so many options it may feel hard to choose the right platform(s) without a good bit of research regarding display, availability of games for a particular platform, how long before the platform starts to become “obsolete”, etc. What we would like to know this week is which gaming platform you prefer. Is there only one that you choose to use or do you use multiple platforms for gaming? Is there a particular reason such as convenience for your choices? You may even be keeping an older platform around just for a certain game (or games) made for it. Are there any recommendations or advice that you would like to share with your fellow readers? Let us know in the comments! How-To Geek Polls require Javascript. Please Click Here to View the Poll. Latest Features How-To Geek ETC HTG Projects: How to Create Your Own Custom Papercraft Toy How to Combine Rescue Disks to Create the Ultimate Windows Repair Disk What is Camera Raw, and Why Would a Professional Prefer it to JPG? The How-To Geek Guide to Audio Editing: The Basics How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 Apture Highlights Turns Your Cursor into a Search Tool Add Classic Sci-Fi Goodness to Your Desktop with the Matrix Theme for Windows 7 You Can’t Walk Straight without Visual Markers [Video] Lord of the Rings Movie Parody Double Feature [Video] Turn a Webpage into an Asteroids-Styled Shooting Game in Opera Dolphin Browser Mini Leaves Beta; Sports New GUI, Easy Bookmarking, and More

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• MacGyver Moments

  - by KKline

  In case you haven't heard, your MacGyver Moments are those times when you improvised an excellent solution to a problem using non-traditional materials, techniques, or tools......(read more)

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• AS11 Oracle B2B Sync Support - Series 1

  - by sinkarbabu.kirubanithi

  Synchronous message support has been enabled in Oracle B2B 11G. This would help customers to send the business message and receive the corresponding business response synchronously. We would like to keep this blog entry as three part series, first one would carry Oracle B2B configuration related details followed by 'how it can be consumed and utilized in an enterprise' using composites backed model. And, the last one would talk about more sophisticated seeded support built on Oracle B2B platform (Note: the last one is still in description phase and ETA hasn't been finalized yet). Details: In an effort to enable synchronous processing in Oracle B2B, we provided a platform using the existing 'callout' mechanism. In this case, we expect the 'callout' attached to the agreement to deliver incoming business message (inbound) to back-end application and get the corresponding business response from back-end and deliver it to Oracle B2B as its output. The output of 'callout' would be processed as outbound message and the same will be attached as a response for the inbound message. Requirements to enable Sync Support: Outbound side: Outbound Agreement - to send business message request Inbound Agreement - to receive business message response Inbound side: Inbound Agreement - to receive business message request Outbound Agreement - to send business message response Agreement Level Callout - to deliver the inbound request to back-end and get the corresponding business response This feature is supported only for HTTP based transport to exchange messages with Trading Partners. One may initiate the outbound message (enqueue) using any of the available Transports in Oracle B2B. Configuration: Outbound side: Please add "syncresponse=true" as "Additional Transport Header" parameter for remote Trading Partner's HTTP delivery channel configuration. This would enable Oracle B2B to process the HTTP response as inbound message and deliver the same to back-end application. All other configuration related to Agreement and Document setup remain same. Inbound side: There is no change in Agreement and Document setup. To enable "Sync Support", you need to build a 'callout' that takes the responsibility of delivering inbound message to back-end and get the corresponding business response from the back-end and attach the same as its output. Oracle B2B treats the output of 'callout' as outbound message and deliver it to Trading Partner as synchronous HTTP response. The requests that needs to processed synchronously should be received by "syncreceiver" (http://:/b2b/syncreceiver) endpoint in Oracle B2B. Exception Handling: Existing Oracle B2B exception handling applies to this use case as well. Here's the sample callout, SampleSyncCallout.java We will get you second part that talks about 'SOA composites' backed model to design the "Sync Support" use case from back-end to Trading Partners, stay tuned.

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• Simplest VoIP Solution Yet?

  MyPhone2Go is fully contained on a portable USB flash drive, can be used with just about any Windows computer.

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• Residential Care Homes website launched based on the Umbraco CMS

  - by Vizioz Limited

  This week we have launched a new website for a local company called Ascot Residential Homes. They run two homes for the elderly and for those who suffer with dementia. Before we built the site for Ascot Residential Homes they asked us to visit the homes to get a feeling about how special they are. If you are looking for a home for an elderly relative I would highly recommend having a look at their website and if you are in the area arranging to visit them.If you look on our site you will also find an Ascot Residential Homes case study in our Umbraco case studies section.

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• Regular expression in Umbraco for number validation.

  - by Vizioz Limited

  This evening I was looking for a way to validate an Umbraco node that could be either text or a numeric value, in my case a salary that could be either an hourly amount, an annual figure or a comment. In the case where the node contained a value I wanted the XSLT to output a pound sign (£) and for any that contained text it would just output the text, as this could be something like "Contact Us" or "Negotiable"I thought someone else might find this useful so here is the XSLT and the regular expression.First if you are using Umbraco, don't forget to include the reference to the EXSLT Regular expression library at the top of your XSLT.<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxml="urn:schemas-microsoft-com:xslt" xmlns:umbraco.library="urn:umbraco.library" xmlns:Exslt.ExsltRegularExpressions="urn:Exslt.ExsltRegularExpressions" exclude-result-prefixes="msxml umbraco.library Exslt.ExsltRegularExpressions">Then the code I used was:<xsl:if test="Exslt.ExsltRegularExpressions:match($currentPage/data [@alias='Salary'], '^[0-9]*\,?[0-9]*\.?[0-9]+$') != ''"> <xsl:text>£</xsl:text></xsl:if>This regular expression allows any number of digits, an optional comma, more digits, an optional decimal point and finally more digits, so all the following are valid:12,00014.43334,342.03

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• OpenGL ES 2.0: Using VBOs?

  - by Bunkai.Satori

  OpenGL VBOs (vertex buffer objects) have been developed to improve performance of OpenGL (OpenGL ES 2.0 in my case). The logic is that with the help of VBOs, the data does not need to be copied from client memory to graphics card on per frame basis. However, as I see it, the game scene changes continuously: position of objects change, their scaling and rotating change, they get animated, they explode, they get spawn or disappear. In such highly dynamic environment, such as computer game scene is, what is the point of using VBOs, if the VBOs would need to be constructed on per-frame basis anyway? Can you please help me to understand how to practically take beneif of VBOs in computer games? Can there be more vertex based VBOs (say one per one object) or there must be always exactly only one VBO present for each draw cycle?

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• Unity3d generating a file in iOS and saving it on a linux machine

  - by N0xus

  I've done a little research and don't know if the following is possible. At the moment I have created a small application in Unity that generates an XML file. This file will be used to help set up my game. It's done in Unity due to it being cross platform with no need to re-write a single line of code. Eventually this will run on an iPad. However, my game will be running on a linux computer and I need to pass over the XML file to the computer that will be running the final game (please don't ask why I'm doing that, it's something I need to do). So what I want to know is the following: Can I generate my XML file on an iPad and have that XML file be saved, and transmitted to a linux machine, without the need to manually copy the file over. If so, how is this possible?

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• Making Thunar the default file browser without hiding the desktop icons

  - by Manu

  I really dislike Ubuntu's default file browser, nautilus, and decided to opt for a lighter alternative (Thunar or Xfe). I've used the following script to change the default to Thunar, but now all my icons are gone from the desktop ! The files are still there, in /home/myid/Desktop, but they do not appear. Is there a way to show them, or is this a consequence of removing nautilus as the default file browser ? Can I modify the following script* in order to keep the icons ? *copied from https://help.ubuntu.com/...: ## Originally written by aysiu from the Ubuntu Forums ## This is GPL'ed code ## So improve it and re-release it ## Define portion to make Thunar the default if that appears to be the appropriate action makethunardefault() { ## I went with --no-install-recommends because ## I didn't want to bring in a whole lot of junk, ## and Jaunty installs recommended packages by default. echo -e "\nMaking sure Thunar is installed\n" sudo apt-get update && sudo apt-get install thunar --no-install-recommends ## Does it make sense to change to the directory? ## Or should all the individual commands just reference the full path? echo -e "\nChanging to application launcher directory\n" cd /usr/share/applications echo -e "\nMaking backup directory\n" ## Does it make sense to create an entire backup directory? ## Should each file just be backed up in place? sudo mkdir nonautilusplease echo -e "\nModifying folder handler launcher\n" sudo cp nautilus-folder-handler.desktop nonautilusplease/ ## Here I'm using two separate sed commands ## Is there a way to string them together to have one ## sed command make two replacements in a single file? sudo sed -i -n 's/nautilus --no-desktop/thunar/g' nautilus-folder-handler.desktop sudo sed -i -n 's/TryExec=nautilus/TryExec=thunar/g' nautilus-folder-handler.desktop echo -e "\nModifying browser launcher\n" sudo cp nautilus-browser.desktop nonautilusplease/ sudo sed -i -n 's/nautilus --no-desktop --browser/thunar/g' nautilus-browser.desktop sudo sed -i -n 's/TryExec=nautilus/TryExec=thunar/g' nautilus-browser.desktop echo -e "\nModifying computer icon launcher\n" sudo cp nautilus-computer.desktop nonautilusplease/ sudo sed -i -n 's/nautilus --no-desktop/thunar/g' nautilus-computer.desktop sudo sed -i -n 's/TryExec=nautilus/TryExec=thunar/g' nautilus-computer.desktop echo -e "\nModifying home icon launcher\n" sudo cp nautilus-home.desktop nonautilusplease/ sudo sed -i -n 's/nautilus --no-desktop/thunar/g' nautilus-home.desktop sudo sed -i -n 's/TryExec=nautilus/TryExec=thunar/g' nautilus-home.desktop echo -e "\nModifying general Nautilus launcher\n" sudo cp nautilus.desktop nonautilusplease/ sudo sed -i -n 's/Exec=nautilus/Exec=thunar/g' nautilus.desktop ## This last bit I'm not sure should be included ## See, the only thing that doesn't change to the ## new Thunar default is clicking the files on the desktop, ## because Nautilus is managing the desktop (so technically ## it's not launching a new process when you double-click ## an icon there). ## So this kills the desktop management of icons completely ## Making the desktop pretty useless... would it be better ## to keep Nautilus there instead of nothing? Or go so far ## as to have Xfce manage the desktop in Gnome? echo -e "\nChanging base Nautilus launcher\n" sudo dpkg-divert --divert /usr/bin/nautilus.old --rename /usr/bin/nautilus && sudo ln -s /usr/bin/thunar /usr/bin/nautilus echo -e "\nRemoving Nautilus as desktop manager\n" killall nautilus echo -e "\nThunar is now the default file manager. To return Nautilus to the default, run this script again.\n" } restorenautilusdefault() { echo -e "\nChanging to application launcher directory\n" cd /usr/share/applications echo -e "\nRestoring backup files\n" sudo cp nonautilusplease/nautilus-folder-handler.desktop . sudo cp nonautilusplease/nautilus-browser.desktop . sudo cp nonautilusplease/nautilus-computer.desktop . sudo cp nonautilusplease/nautilus-home.desktop . sudo cp nonautilusplease/nautilus.desktop . echo -e "\nRemoving backup folder\n" sudo rm -r nonautilusplease echo -e "\nRestoring Nautilus launcher\n" sudo rm /usr/bin/nautilus && sudo dpkg-divert --rename --remove /usr/bin/nautilus echo -e "\nMaking Nautilus manage the desktop again\n" nautilus --no-default-window & ## The only change that isn't undone is the installation of Thunar ## Should Thunar be removed? Or just kept in? ## Don't want to load the script with too many questions? } ## Make sure that we exit if any commands do not complete successfully. ## Thanks to nanotube for this little snippet of code from the early ## versions of UbuntuZilla set -o errexit trap 'echo "Previous command did not complete successfully. Exiting."' ERR ## This is the main code ## Is it necessary to put an elseif in here? Or is ## redundant, since the directory pretty much ## either exists or it doesn't? ## Is there a better way to keep track of whether ## the script has been run before? if [[ -e /usr/share/applications/nonautilusplease ]]; then restorenautilusdefault else makethunardefault fi;

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• Guidance and Pricing for MSDN 2010

  - by John Alexander

  Sorry for the rather lengthy post here. I get asked this all the time so I decided to post it…Visual Studio 2010 editions will be available on April 12, 2010. Product Features Professional with MSDN Essentials Professional with MSDN Premium with MSDN Ultimate with MSDN Test Professional with MSDN Debugging and Diagnostics IntelliTrace (Historical Debugger)         Static Code Analysis       Code Metrics       Profiling       Debugger   Testing Tools Unit Testing   Code Coverage       Test Impact Analysis       Coded UI Test       Web Performance Testing         Load Testing1         Microsoft Test Manager 2010       Test Case Management2       Manual Test Execution       Fast-Forward for Manual Testing       Lab Management Configuration3       Integrated Development Environment Multiple Monitor Support   Multi-Targeting   One Click Web Deployment   JavaScript and jQuery Support   Extensible WPF-Based Environment Database Development Database Deployment       Database Change Management2       Database Unit Testing       Database Test Data Generation       Data Access   Development Platform Support Windows Development   Web Development   Office and SharePoint Development   Cloud Development   Customizable Development Experience   Architecture and Modeling Architecture Explorer         UML® 2.0 Compliant Diagrams (Activity, Use Case, Sequence, Class, Component)         Layer Diagram and Dependency Validation         Read-only diagrams (UML, Layer, DGML Graphs)         Lab Management Virtual environment setup & tear down3       Provision environment from template3       Checkpoint environment3       Team Foundation Server Version Control2   Work Item Tracking2   Build Automation2   Team Portal2   Reporting & Business Intelligence2   Agile Planning Workbook2   Microsoft Visual Studio Team Explorer 2010   Test Case Management2       MSDN Subscription – Software and Services for Production Use Windows Azure Platform 20 hrs/mo † 50 hrs/mo † 100 hrs/mo † 250 hrs/mo † n/a Microsoft Visual Studio Team Foundation Server 2010   Microsoft Visual Studio Team Foundation Server 2010 CAL   1 1 1 1 Microsoft Expression Studio 3       Microsoft Office Professional Plus 2010, Project Professional 2010, Visio Premium 2010 (following Office 2010 launch)       MSDN Subscription – Software for Development and Testing 4 Windows 7, Windows Server 2008 R2 and SQL Server 2008 Toolkits, Software Development Kits, Driver Development Kits Previous versions of Windows (client and server operation systems)   Previous versions of Microsoft SQL Server   Microsoft Office       Microsoft Dynamics       All other Servers       Windows Embedded operating systems       Teamprise         MSDN Subscription – Other Benefits Technical support incidents 0 2 4 4 2 Priority support in MSDN Forums Microsoft e-learning collections (typically 10 courses or 20 hours) 0 1 2 2 1 MSDN Flash newsletter MSDN Online Concierge MSDN Magazine   System Requirements View View View View View Buy from (MSRP) $799 $1,199 $5,469 $11,899 $2,169 Renew from (MSRP) $549 (upgrade) $799 $2,299 $3,799 $899 † Availability varies by country and subscription level.  Details available on the MSDN site 1. May require one or more Microsoft Visual Studio Load Test Virtual User Pack 2010 2. Requires Team Foundation Server and a Team Foundation Server CAL 3. Requires Microsoft Visual Studio Lab Management 2010 4. Per-user license allows unlimited installations and use for designing, developing, testing, and demonstrating applications. UML is a registered trademark of Object Management Group, Inc. Windows is either a registered trademark or trademark of Microsoft Corporation in the United States and/or other countries.

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• Following the Thread in OSB

  - by Antony Reynolds

  Threading in OSB The Scenario I recently led an OSB POC where we needed to get high throughput from an OSB pipeline that had the following logic: 1. Receive Request 2. Send Request to External System 3. If Response has a particular value   3.1 Modify Request   3.2 Resend Request to External System 4. Send Response back to Requestor All looks very straightforward and no nasty wrinkles along the way.  The flow was implemented in OSB as follows (see diagram for more details): Proxy Service to Receive Request and Send Response Request Pipeline   Copies Original Request for use in step 3 Route Node   Sends Request to External System exposed as a Business Service Response Pipeline   Checks Response to Check If Request Needs to Be Resubmitted Modify Request Callout to External System (same Business Service as Route Node) The Proxy and the Business Service were each assigned their own Work Manager, effectively giving each of them their own thread pool. The Surprise Imagine our surprise when, on stressing the system we saw it lock up, with large numbers of blocked threads.  The reason for the lock up is due to some subtleties in the OSB thread model which is the topic of this post.   Basic Thread Model OSB goes to great lengths to avoid holding on to threads.  Lets start by looking at how how OSB deals with a simple request/response routing to a business service in a route node. Most Business Services are implemented by OSB in two parts.  The first part uses the request thread to send the request to the target.  In the diagram this is represented by the thread T1.  After sending the request to the target (the Business Service in our diagram) the request thread is released back to whatever pool it came from.  A multiplexor (muxer) is used to wait for the response.  When the response is received the muxer hands off the response to a new thread that is used to execute the response pipeline, this is represented in the diagram by T2. OSB allows you to assign different Work Managers and hence different thread pools to each Proxy Service and Business Service.  In out example we have the “Proxy Service Work Manager” assigned to the Proxy Service and the “Business Service Work Manager” assigned to the Business Service.  Note that the Business Service Work Manager is only used to assign the thread to process the response, it is never used to process the request. This architecture means that while waiting for a response from a business service there are no threads in use, which makes for better scalability in terms of thread usage. First Wrinkle Note that if the Proxy and the Business Service both use the same Work Manager then there is potential for starvation.  For example: Request Pipeline makes a blocking callout, say to perform a database read. Business Service response tries to allocate a thread from thread pool but all threads are blocked in the database read. New requests arrive and contend with responses arriving for the available threads. Similar problems can occur if the response pipeline blocks for some reason, maybe a database update for example. Solution The solution to this is to make sure that the Proxy and Business Service use different Work Managers so that they do not contend with each other for threads. Do Nothing Route Thread Model So what happens if there is no route node?  In this case OSB just echoes the Request message as a Response message, but what happens to the threads?  OSB still uses a separate thread for the response, but in this case the Work Manager used is the Default Work Manager. So this is really a special case of the Basic Thread Model discussed above, except that the response pipeline will always execute on the Default Work Manager.   Proxy Chaining Thread Model So what happens when the route node is actually calling a Proxy Service rather than a Business Service, does the second Proxy Service use its own Thread or does it re-use the thread of the original Request Pipeline? Well as you can see from the diagram when a route node calls another proxy service then the original Work Manager is used for both request pipelines.  Similarly the response pipeline uses the Work Manager associated with the ultimate Business Service invoked via a Route Node.  This actually fits in with the earlier description I gave about Business Services and by extension Route Nodes they “… uses the request thread to send the request to the target”. Call Out Threading Model So what happens when you make a Service Callout to a Business Service from within a pipeline.  The documentation says that “The pipeline processor will block the thread until the response arrives asynchronously” when using a Service Callout.  What this means is that the target Business Service is called using the pipeline thread but the response is also handled by the pipeline thread.  This implies that the pipeline thread blocks waiting for a response.  It is the handling of this response that behaves in an unexpected way. When a Business Service is called via a Service Callout, the calling thread is suspended after sending the request, but unlike the Route Node case the thread is not released, it waits for the response.  The muxer uses the Business Service Work Manager to allocate a thread to process the response, but in this case processing the response means getting the response and notifying the blocked pipeline thread that the response is available.  The original pipeline thread can then continue to process the response. Second Wrinkle This leads to an unfortunate wrinkle.  If the Business Service is using the same Work Manager as the Pipeline then it is possible for starvation or a deadlock to occur.  The scenario is as follows: Pipeline makes a Callout and the thread is suspended but still allocated Multiple Pipeline instances using the same Work Manager are in this state (common for a system under load) Response comes back but all Work Manager threads are allocated to blocked pipelines. Response cannot be processed and so pipeline threads never unblock – deadlock! Solution The solution to this is to make sure that any Business Services used by a Callout in a pipeline use a different Work Manager to the pipeline itself. The Solution to My Problem Looking back at my original workflow we see that the same Business Service is called twice, once in a Routing Node and once in a Response Pipeline Callout.  This was what was causing my problem because the response pipeline was using the Business Service Work Manager, but the Service Callout wanted to use the same Work Manager to handle the responses and so eventually my Response Pipeline hogged all the available threads so no responses could be processed. The solution was to create a second Business Service pointing to the same location as the original Business Service, the only difference was to assign a different Work Manager to this Business Service.  This ensured that when the Service Callout completed there were always threads available to process the response because the response processing from the Service Callout had its own dedicated Work Manager. Summary Request Pipeline Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Route Node Request sent using Proxy WM Thread Proxy WM Thread is released before getting response Muxer is used to handle response Muxer hands off response to Business Service (BS) WM Response Pipeline Executes on Routed Business Service WM Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. No Route Node (Echo functionality) Proxy WM thread released New thread from the default WM used for response pipeline Service Callout Request sent using proxy pipeline thread Proxy thread is suspended (not released) until the response comes back Notification of response handled by BS WM thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Note this is a very short lived use of the thread After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread. Route/Callout to Proxy Service Request Pipeline of callee executes on requestor thread Response Pipeline of caller executes on response thread of requested proxy Throttling Request message may be queued if limit reached. Requesting thread is released (route node) or suspended (callout) So what this means is that you may get deadlocks caused by thread starvation if you use the same thread pool for the business service in a route node and the business service in a callout from the response pipeline because the callout will need a notification thread from the same thread pool as the response pipeline.  This was the problem we were having. You get a similar problem if you use the same work manager for the proxy request pipeline and a business service callout from that request pipeline. It also means you may want to have different work managers for the proxy and business service in the route node. Basically you need to think carefully about how threading impacts your proxy services. References Thanks to Jay Kasi, Gerald Nunn and Deb Ayers for helping to explain this to me.  Any errors are my own and not theirs.  Also thanks to my colleagues Milind Pandit and Prasad Bopardikar who travelled this road with me. OSB Thread Model Great Blog Post on Thread Usage in OSB

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• SQL SERVER – Find Weekend and Weekdays from Datetime in SQL Server 2012

  - by pinaldave

  Yesterday we had very first SQL Bangalore User Group meeting and I was asked following question right after the session. “How do we know if today is a weekend or weekday using SQL Server Functions?” Well, I assume most of us are using SQL Server 2012 so I will suggest following solution. I am using SQL Server 2012′s CHOOSE function. It is SELECT GETDATE() Today, DATENAME(dw, GETDATE()) DayofWeek, CHOOSE(DATEPART(dw, GETDATE()), 'WEEKEND','Weekday', 'Weekday','Weekday','Weekday','Weekday','WEEKEND') WorkDay GO You can use the choose function on table as well. Here is the quick example of the same. USE AdventureWorks2012 GO SELECT A.ModifiedDate, DATENAME(dw, A.ModifiedDate) DayofWeek, CHOOSE(DATEPART(dw, A.ModifiedDate), 'WEEKEND','Weekday', 'Weekday','Weekday','Weekday','Weekday','WEEKEND') WorkDay FROM [Person].[Address] A GO If you are using an earlier version of the SQL Server you can use a CASE statement instead of CHOOSE function. Please read my earlier article which discusses CHOOSE function and CASE statements. Logical Function – CHOOSE() – A Quick Introduction Reference:  Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL DateTime, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• The Beginner’s Guide To Tabbed Browsing

  - by Chris Hoffman

  Tabs allow you to open multiple web pages in a single browser window without cluttering your desktop. Mastering tabbed browsing can speed up your browsing experience and make multiple web pages easier to manage. Tabbed browsing was once the domain of geeks using alternative browsers, but every popular browser now supports tabbed browsing – even mobile browsers on smartphones and tablets. This article is intended for beginners. If you know someone that doesn’t fully understand tabbed browsing and how awesome it is, feel free to send it to them! How Hackers Can Disguise Malicious Programs With Fake File Extensions Can Dust Actually Damage My Computer? What To Do If You Get a Virus on Your Computer

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• How to Connect Your Android to Your PC’s Internet Connection Over USB

  - by Chris Hoffman

  People often “tether” their computers to their smartphones, sending their computer’s network traffic over the device’s cellular data connection. “Reverse tethering” is the opposite – tethering your Android smartphone or tablet to your PC to use your PC’s Internet connection. This method requires a rooted Android and a Windows PC, but it’s very easy to use. If your computer has Wi-Fi, it may be easier to create a Wi-Fi hotspot using a utility like Connectify instead. How to Make Your Laptop Choose a Wired Connection Instead of Wireless HTG Explains: What Is Two-Factor Authentication and Should I Be Using It? HTG Explains: What Is Windows RT and What Does It Mean To Me?

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• how to access inaccessible mac os x hard drive via ubuntu

  - by jon

  Background: My intention was to load a Virtual Machine (VM) on my Mac OS X Snow Leopard. My Mac had just enough room for a VM (my thought process was that VM was the same as partition) However, I burned the newest version of Ubuntu onto a CD, thinking that partitioning and running a virtual machine would be the same. I would restart my computer, booting up Ubuntu installer. The installation would not allow me to partition, forcing me to force shutdown my laptop. when I turn on my laptop, I see that my computer is "missing operating system". So, can someone help me fix my a) bootcamp, b) getting files and if a and b are fixed c) to install ubuntu as a VM?

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• Fix: SqlDeploy Task Fails with NullReferenceException at ExtractPassword

  Still working on getting a TeamCity build working (see my last post).  Latest exception is: C:\Program Files\MSBuild\Microsoft\VisualStudio\v9.0\TeamData\Microsoft.Data.Schema.SqlTasks.targets(120, 5): error MSB4018: The "SqlDeployTask" task failed unexpectedly. System.NullReferenceException: Object reference not set to an instance of an object. at Microsoft.Data.Schema.Common.ConnectionStringPersistence.ExtractPassword(String partialConnection, String dbProvider) at Microsoft.Data.Schema.Common.ConnectionStringPersistence.RetrieveFullConnection(String partialConnection, String provider, Boolean presentUI, String password) at Microsoft.Data.Schema.Sql.Build.SqlDeployment.ConfigureConnectionString(String connectionString, String databaseName) at Microsoft.Data.Schema.Sql.Build.SqlDeployment.OnBuildConnectionString(String partialConnectionString, String databaseName) at Microsoft.Data.Schema.Build.Deployment.FinishInitialize(String targetConnectionString) at Microsoft.Data.Schema.Build.Deployment.Initialize(FileInfo sourceDbSchemaFile, ErrorManager errors, String targetConnectionString) at Microsoft.Data.Schema.Build.DeploymentConstructor.ConstructServiceImplementation() at Microsoft.Data.Schema.Extensibility.ServiceConstructor'1.ConstructService() at Microsoft.Data.Schema.Tasks.DBDeployTask.Execute() at Microsoft.Build.BuildEngine.TaskEngine.ExecuteInstantiatedTask(EngineProxy engineProxy, ItemBucket bucket, TaskExecutionMode howToExecuteTask, ITask task, Boolean& taskResult)   This time searching yielded some good stuff, including this thread that talks about how to resolve this via permissions.  The short answer is that the account that your build server runs under needs to have the necessary permissions in SQL Server.  Youll need to create a Login and then ensure at least the minimum rights are configured as described here: Required Permissions in Database Edition Alternately, you can just make your buildserver account an admin on the database (which is probably running on the same machine anyway) and at that point it should be able to do whatever it needs to. If youre certain the account has the necessary permissions, but youre still getting the error, the problem may be that the account has never logged into the build server.  In this case, there wont be any entry in the HKCU hive in the registry, which the system is checking for permissions (see this thread).  The solution in this case is quite simple: log into the machine (once is enough) with the build server account.  Then, open Visual Studio (thanks Brendan for the answer in this thread). Summary Make sure the build service account has the necessary database permissions Make sure the account has logged into the server so it has the necessary registry hive info Make sure the account has run Visual Studio at least once so its settings are established In my case I went through all 3 of these steps before I resolved the problem. 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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