How do 2PC prevent commit failure?
How do distributed transactions work (eg. MSDTC)?
Expressing using properties of vectors It is given in question that $x+a=(a.x)b$ and it is stated that a,b and x are vectors.It is also stated that $a.b$ not equal to $1$.The question ask to express $x$ in term $a$ and $b$,how do you this? How can I get a more traditional drop-down like menu for Unity? Double Whatsapp Backup in iCloud I am not sure if this is the case, but when you do iCloud Backup of your phone, it will backup Whatsapp. ( I am unsure if this include the Photos and Video )   Then Whatsapp itself has backup option to backup itself in iCloud Drive Backup.   Is that a double Backup? Because i see 2.1GB inside the iCloud Backup, and then 1.7Gb inside document and settings. "The train will leave" vs. "is going to leave" vs. "leaves" vs. "is leaving" From the grammatical point of view all are correct, just the meaning are different, please bring your clarification, thank you.        The Train will leave at 10:00 tomorrow morning.   The Train is going to leave at 10:00 tomorrow morning.   The Train leaves at 10:00 tomorrow morning.   The Train is leaving at 10:00 tomorrow morning. How to set system-wide environment variables on OS X Mavericks How to evaluate $ \lim \limits_{n\to \infty} \sum \limits_ {k=1}^n \frac{k^n}{n^n}$? I can show that the following limit exists but I am having difficulties to find it. It is $$\lim_{n\to \infty} \sum_{k=1}^n \frac{k^n}{n^n}$$ Can someone please help me? What is the best place for storing binary files that are related to data in your database? Should you:   Store in the database with a blob Store on the filesystem with a link in the database Store in the filesystem but rename to a hash of the contents and store the hash on the database Something I've not thought of   The advantages of (1) are (among others) that atomicity of transactions is preserved. The cost is that you might dramatically increase storage (and associated streaming/backup) requirements  The goal of (3) is to preserve atomicity to some degree - if you can enforce that the filesystem you are writing to does not allow files to be changed or deleted, and always has the correct hash as filename. The idea would be to write the file to the filesystem before permitting the insert/update referencing the hash - if this transaction fails after the filesystem write but before the database DML, that is fine because the filesystem is 'faking' being the repository of all possible files and hashes - it doesn't matter if there are some files in there that are not being pointed to (and you could clean them up periodically if you are careful)  EDIT:  It looks like some RDBMSs have this covered in their individual ways - I'd be interested to know how others do it - and particularly in a solution for postgres What's the difference between the apt packages: 'cinnamon' and 'cinnamon-desktop-environment'? I have a fresh Ubuntu install and want to install Cinnamon as the desktop environment. When I do apt search cinnamon, I get multiple results, but two seems like they are the correct one.   The first is just   cinnamon/xenial 2.8.6-1ubuntu1 amd64 all     Innovative and comfortable desktop (Common data files)   while the other is   cinnamon-desktop-environment/xenial,xenial 2.8.0 all     Cinnamon desktop environment - full desktop with extra components   What's the difference between the two? What does the cinnamon-desktop-environment package contain that the cinnamon doesn't? New SSD problem I've just installed a new SSD replacing an HDD in my old (late 2008) iMac. When I switched it on all I got on screen was a question mark.   On the advice of my son I tried cmdR during switch on with no result.   I then tried alt which at least got me a cursor on the screen, but nothing else. Any suggestions? I've got everything backed up on an external Hard Drive, by the way. Identify this novel: youngsters psychologically tested for abilities/profession, hero wants to author the tests, society uses moving walkways Mrs Reed safe combination Mrs Reed forgets the number combination to her safe. The combination has $4$ numbers each is a $1$ digit number. The $4$ digits add up to $10$ and there are no zeros. How many times does Mrs Reed have to try to open her safe?  My attempt: ${9 \choose 3} = 84$ but the answer is $80$. Perfect set without rational numbers Sorry if this problem is repeated.  Is there a nonempty perfect set in $\mathbb{R}^1$ which contains no rational number?  Proof sketch: This set must be uncountable because any nonempty perfect set in $\mathbb{R}^k$ is uncountable.   We know that Cantor set (C) is perfect set on a line. If we take $E=C+\sqrt{2}=\{x+\sqrt{2}: x\in C\}$. Will this set be an answer to above problem? How to automatically reinvest in non-dividend paying funds I've read Einsteins quote stating "The most powerful force in the universe is compound interest." However, everywhere I read this is basically only possible with dividend paying stocks and then applying a dividend reinvestment plan.  Is there a re-investing strategy like this for non-dividend paying mutual funds (or even non-dividend paying stock)? I figured that the only way would be to sell all your funds and then buy x+1 funds again, but this would cause a big loss because of transaction costs from the broker. What is a wave? How do electric currents make light? In an incandescent light bulb, electrons flow through wires to the bulb, where is passes through a filament, and the filament lights up.  Does this work because of several high energy electrons losing some of their energy to disturb the electromagnetic field, creating photons? The electrons just leave the filament afterward and are replaced by more high-energy electrons from the negative terminal. Or does it work differently?  As a secondary question, is there a type of light bulb that directly converts electron flow to photons? Setting Objects to Null/Nothing after use in .NET How to make a model cast shadows onto the world texture/background? In most of my models, I usually end up setting a world background using an HDRI image of some kind or another. This has always been really useful for lighting in general or as a background for my final render.  But what if I want my model to look like it is interacting or touching part of the background? For example, in the image below that I found, the modeled objects look like they're part of the scene, and even appear to cast shadows on the ground. How can I do this? Show the commutator subgroup of $S_{n}$ is $A_{n}$ for $n \geq 5$ Show that for $n \geq 5$, the commutator subgroup of $S_{n}$ is $A_{n}$ for $n \geq 5$.     I'm not sure on how to handle this problem. I know that the commutator subgroup $G'$ will consist of products of commutators $[\sigma_{i}, \tau_{i}]$ for permutations $\sigma_{i}, \tau_{i} \in S_{n}$. However, I don't know where to start. What would be the best way to approach this? Where can I find Vagrant packages? is a tool to build and manage virtual machines for developers.  It has a  guide that contains iffy-looking suggestions like  $ sudo ln -s /usr/bin/ruby1.8 /usr/bin/ruby  # wtf???   or installing RubyGems from source rather than from Ubuntu packages, and then using gem install to install vagrant itself.  I'm not feeling comfortable just following those instructions.  Is there perhaps a PPA?  Are there, perhaps, alternative tools that are packaged for Ubuntu? How can I find the cheapest prepaid SIM card for a given country?