in-memory-database

I was just think that now it is common to have enough RAM on your database server to cache your complete database why are the specialist in memory database (e.g TimesTen , see also Wikipedia page ) that were all the rage a few years ago not being used more? It seems to be that as time go on, none disk based databases are being used less, e.g most applications are now built on conventional rational databases. I would have expected the opposite as RAM is getting close to being free for a lot of servers. I am asking this, as I just read up on the stack-overflow-architecture and the page says This

This question already has answers here : Embedded MongoDB when running integration tests (13 answers) Possible Duplicate: Embedded MongoDB when running integration tests I want to use In-Memory mode for unit test, is there an in In-Memory mode like RavenDB? Dmitry Reznik There is no in-memory mode for MongoDB. As per this link, this feature won't be included until at least MongoDB 2.8. Though since it's using Memory-mapped IO, it should be as speedy as in-memory during the actual processing. Not the startup though. Also, there's a hack to use RAM disk drive and put your mongo db there. That

I find it very common to want to model relational data in my functional programs. For example, when developing a web-site I may want to have the following data structure to store info about my users: data User = User { name :: String , birthDate :: Date } Next, I want to store data about the messages users post on my site: data Message = Message { user :: User , timestamp :: Date , content :: String } There are multiple problems associated with this data structure: We don't have any way of distinguishing users with similar names and birth dates. The user data will be duplicated on

I have an application where many "unit" tests use a real connection to an Oracle database during their execution. As you can imagine, these tests take too much time to be executed, as they need to initialize some Spring contexts, and communicate to the Oracle instance. In addition to that, we have to manage complex mechanisms, such as transactions, in order to avoid database modifications after the test execution (even if we use usefull classes from Spring like AbstractAnnotationAwareTransactionalTests ). So my idea is to progressively replace this Oracle test instance by an in-memory database

I am using HSQL in memory database for test purpose of my application and using SQL Server as main database, now when am doing test then HSQL Database is being populated with same data that I have in my SQL Server, now I am trying to test particular service which is retrieving data from Database(it would query MS Server if directly service is run or it will query HSQL Database if called from test) I am able to see data from MS Server when I run the query but HSQL Db does not return any data if am running same query on it. My hunch here is that HSQL DB is not being populated with the data, is

HttpSession is a high level interface built on top of cookies and url-rewriting, which means that there is only a session ID is stored in client side and the data associated with it is stored in server side. Where is the HttpSession data actually stored in the server side? In the JVM memory or somewhere else? Can I change the place where to store it, e.g. save them into an in-memory database? If it's not in a database, is there any concurrency problem when many clients work on the same session data at the same time? It's up to the server where to store session data; the ones I'm familiar with